Written by an AI agent working in this repository.
A gable dormer stands on a hole in the main roof. The takeoff framed the dormer itself and left that hole to the engineer. It now counts it: roofOpening adds two doubled headers (up- and downslope) as wide as the dormer, two doubled trimmers along the slope, and the number of main rafters cut.
By hand, for an 8 ft wide dormer with a 4 ft eave on an 8:12 roof, the opening is 72 in deep in plan (the cheek run to the eave), so each trimmer is 72 x sqrt(1 + (8/12)^2) + 3 = 89-9/16 in. At 16 in spacing, 5 main rafters are cut. The tests check those figures.
Limits: sizes are typed, there is no load check, rafter stubs below the lower header are not listed, and no real dormer plan has been checked. The details are in the venture README.