Tromp as Writ is a weaving term that means treadle as written in the weaving draft; the shaft numbers used in the threading are used to generate the treadle numbers in the weft.
In TempoWeave, when this option is selected from the Tools command, you are first given a prompt as to whether or not to include structure only, structure and color or color only. Structure replacement means that the shaft number for each thread becomes the corresponding treadle for each weft pick. If there were more weft picks than warp threads prior to executing Tromp as Writ with structure, then the weft picks after executing the commond will equal the number of warp threads. If color only is copied, the treadling is not changed.
In the following example, tromp as writ has been applied to structure and color to produce a perfectly square cloth where the warp and weft colors as are in the same sequence and the treadle numbers for each pick are the same as the shaft numbers.
Another use of Tromp as Writ, especially for Dobby looms with a high number of shafts, is to create a draft whereby you can treadle the threading.
First save your design under another name using "File | Save As" . You may want to add "threading" to the file name to avoid confusion. Next, do Tromp as Writ with Structure and Color and save your threading draft.
While threading the loom, press the dobby treadle for each warp thread, raising a single shaft at a time, verifying that the color called for i the color you are threading through the heddle.