Block Substitution
What It Does
Block Substitution takes a simple profile draft and expands it into a full weave structure by applying a weave template. Your profile draft defines the block layout — which blocks are active where — and the template defines how each block is actually woven (the specific interlacement, tie-down threads, and shaft assignments within each block).
This is how weavers traditionally work with block weaves: you design the pattern at the block level (simple, fast), then substitute in the actual weave structure (Huck, Overshot, Summer and Winter, etc.) to produce the full threading, tie-up, and treadling needed at the loom.
Location
Ribbon: Design tab > Section Assembly group > Block Substitution button (toggle)
The Block Substitution panel opens as a dockable tool window.
The Panel
Template List
The upper portion shows all available weave templates in a list with columns:
Name — Template name (e.g., "Spot Bronson," "Summer and Winter 4-Block," "Deflected Double Weave")
Type — Weave category (Huck, Overshot, Summer and Winter, Deflected Double, etc.)
Shafts — Number of shafts in the template pattern
Treadles — Number of treadles per block
Click a template to select it and see its details in the info panel below.
Template Management
Add — Create a new template entry. Opens the template editor.
Edit — Modify the selected template's settings. The editor also offers two buttons next to the File Name field:
…Browse — Pick a.wiffrom anywhere on disk; the file is copied into the templates folder for you.✎Edit Template WIF — Open the selected template's.wifin a new editor tab so you can change threading / treadling / tieup directly. Saving in that tab writes back to the templates folder, so the next Apply picks up the edits automatically. Especially useful on macOS where the_blocktemplatesfolder lives inside the invisible~/Librarydirectory.↺Reset to Bundled — Restore a bundled template's.wif(and matching PNG preview) from the version that shipped with the app. Auto-hidden for user-added templates that have no bundled source.
Delete — Remove the selected template from the library.
Reveal Folder — Open the per-platform templates folder in Finder / Explorer / your file manager. Drop additional .wif files in directly if you prefer to work outside the dialog.
Info Panel
The lower portion shows details about the selected template:
Template Name — Bold, full display
Type — The weave family
Stats:
Shafts (in the template)
Treadles per Block
Tie Shafts (warp tie-down thread count)
Tie Treadles (weft tie treadle count)
Special Properties (when applicable):
Huck Style (Type A, B, C, or D)
Has Weft Background
Tie-up Pattern Reverse
Pattern Warp Wrap
Pattern Step value
Preview Image — A small visual showing what the template's weave pattern looks like
Apply Button
Generates the expanded draft from the selected template applied to your profile.
How It Works
What You Need: A Profile Draft
A profile draft is a simplified block representation of your design. Each shaft represents a "block" and each treadle represents a block activation. For example, a 2-block profile draft has 2 shafts and 2 treadles, with a simple tie-up showing which blocks are active.
The profile defines where each block appears in the design — the template defines how each block is woven.
The profile can be either a tie-up draft or a liftplan draft:
Tie-up profiles — Each pick presses a treadle, and the tie-up says which blocks that treadle activates. Picks that press more than one treadle activate all of their blocks at once.
Liftplan profiles — Each shaft is a block, and each pick simply lifts the block(s) it activates. A pick lifting shafts 1 and 3 weaves pattern in blocks A and C together. Liftplan profiles produce a liftplan result: the generated draft comes out as a liftplan too, ready for dobby looms, with each pick lifting the combined shafts of its expanded structure.
The Substitution Process
When you click Apply, the generator:
Reads your profile draft — Identifies the block layout from your threading and treadling + tie-up (or liftplan)
Reads the template — Loads the template's weave structure, including its threading pattern, treadling, and tie-up
Builds shaft and treadle maps — Determines how the template's shafts and treadles are distributed across your profile blocks:
Tie shafts/treadles are shared across all blocks (they provide the ground structure)
Pattern shafts/treadles are multiplied per block (each block gets its own set)
Expands the threading — Each profile thread is expanded into the template's threading pattern, mapped to the correct shaft group for that block
Builds the tie-up — The template's tie-up is expanded across all block combinations, with special handling for Huck variants, weft backgrounds, and other template-specific rules
Expands the treadling — Each profile pick is expanded into the template's treadling pattern, mapped to the correct treadle group
Creates the output — A new WIF file with the complete expanded structure
Template Types
Different template types have different substitution rules:
Bronson / Bateman — Spot-pattern weaves where a base of plain weave alternates with isolated pattern floats.
Crackle — A 4-shaft block weave with a broken-twill texture that gives the weave its name.
Huck — Lace-producing templates with tie shafts and pattern shafts. Four variants (A, B, C, D) control whether blocks produce lace openings, warp floats, weft floats, or opposite-parity lace.
Overshot — Traditional American block weave with pattern floats over a plain weave ground. Uses stepping patterns and block sequences.
Summer and Winter / 3 Tie / 4 Tie / Double Two Tie — Tie-unit weaves with independent pattern blocks. Produce reversible fabric; the number of tie shafts in the name corresponds to the per-block tie count.
Diversified Plain — A multi-block weave alternating fine and coarse threads to produce distinct color blocks against a plain-weave ground.
Double Weave — Two interleaved cloths joined at block boundaries.
Custom — User-defined templates that follow the general shaft/treadle mapping rules.
The Template Editor
When adding or editing a template:
Name — A descriptive name for the template.
File Name — The WIF file containing the template's weave structure. Click Browse to select a file.
Type — The weave family (Huck, Overshot, Summer and Winter, Double Weave, Custom, etc.).
Template Shafts — Total shafts in the template pattern.
Block Treadles — Treadles per block in the pattern.
Warp Tie Count — Number of tie-down shaft rows.
Weft Tie Treadles — Number of tie treadles.
Pattern Warp Step — For overshot patterns, the step value for progressive shaft assignment.
Weft Background — The template has a separate background pattern for non-active blocks.
Tie-up Pattern Reverse — Inverts the block selection logic in the tie-up.
Pattern Warp Wrap — Wraps pattern shafts when they exceed the maximum, preventing shaft overflow.
Huck Style — Enables special Huck lace handling. Choose variant A, B, C, or D.
How to Use It
Create a profile draft — Set up a simple block design:
Thread with shaft numbers representing blocks (shaft 1 = block A, shaft 2 = block B, etc.)
Treadle with treadle numbers representing block activations
Set up a tie-up showing which blocks are active for each treadle
Or, in a liftplan draft, just lift each pick's block shaft(s) — no tie-up needed
Open Block Substitution from the Design tab
Browse the template library — Click templates to see their details and preview
Select a template that matches the weave you want
Click Apply
The generated draft opens as a preview — review the expanded threading, tie-up, and treadling
Save the generated draft if satisfied
Step-by-Step Example: Huck Lace from a Profile
You have a 3-block profile draft for a lace scarf and want to apply a Huck lace template:
Your profile has 3 shafts (3 blocks), 3 treadles, and a simple tie-up
Open Block Substitution
Select a Huck template (e.g., "Huck Lace 8-Shaft, Type A")
The info panel shows: 8 shafts, 4 treadles per block, 2 tie shafts, Huck Style Type A
Click Apply
The generator creates a full draft with:
Threading: tie-down threads + pattern threads for each of the 3 blocks
Tie-up: Huck lace connections for all block combinations
Treadling: expanded treadle sequence
Review and save
Step-by-Step Example: Overshot from a Simple Profile
You have a 4-block profile and want traditional overshot:
Thread your profile: 4 shafts representing 4 blocks
Design a simple treadling sequence in the profile
Open Block Substitution, select an Overshot template
Apply — the generator expands each profile block into the overshot threading pattern with tabby ties and pattern treadles
The result is a complete overshot draft ready for the loom
Tips
Profile drafts are simple — Keep your profile draft minimal: one shaft per block, one treadle per block activation. The template handles all the complexity.
Preview before saving — Generated drafts open as unsaved previews. Review the structure before committing.
Try different templates — Apply different templates to the same profile to compare how the same block layout looks in Huck vs. Overshot vs. Summer and Winter.
Huck variants matter — The four Huck types (A, B, C, D) produce very different fabrics from the same profile. Type A gives lace, Type B gives warp floats, Type C gives weft floats, Type D gives opposite-parity lace.
Check shaft limits — Block substitution can produce drafts with many shafts (blocks × pattern shafts + tie shafts). Make sure the result fits your loom. The maximum is 128 shafts.
Custom templates — You can create your own templates by designing a weave structure in a WIF file and adding it to the template library with the appropriate settings.
Template files — Templates are stored as WIF files in the templates folder. The template library catalog is saved automatically.
Going Deeper: Authoring Templates
To edit the bundled templates, or author new ones for the Complex Weavers community (or your own block-substitution library), see the companion Block Substitution Authoring Guide. It covers:
Where the templates live on each operating system
The anatomy of a template WIF, including the
*WarpPattern/*TieShaftssection markersWhat each flag in the editor (Block Treadles, Warp Tie Count, Pattern Warp Step, Pattern Warp Wrap, Weft Background, Tie-up Pattern Reverse, Huck Style) actually does to the output
Step-by-step walkthroughs for editing a bundled template and building a new one from scratch
The new Edit Template WIF (
✎) and Reset to Bundled (↺) buttons in the Edit Templates dialogA troubleshooting playbook for the common authoring mistakes
Quick Reference
Open panel
Design tab > Block Substitution (toggle)
Select template
Click in template list
View details
See info panel below list
Apply template
Click Apply button
Add template
Click Add, configure in editor
Edit template
Select + click Edit
Delete template
Select + click Delete
1 shaft per block
Multiple shafts per block + tie shafts
1 treadle per activation
Multiple treadles per block + tie treadles
Simple tie-up
Full expanded tie-up with block interactions
N threads
N × template pattern width threads
Huck
Lace with tie-down threads, 4 variants
Overshot
Pattern floats over plain weave ground
Summer and Winter
Reversible, independent blocks
Custom
User-defined substitution rules
Start with a Profile Draft to use Block Substitution:
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