Birdsmouth

A birdsmouth is a V-shaped notch across the full width of a rafter or purlin, so it sits flat on its support.

Depth 20 mm

Depth 45 mm

Depth 70 mm

Birdsmouth. Drawn by the editor's own geometry code; right: the carved part in 3D.

When to use it

Use a birdsmouth where a sloped rafter rests on a wall plate or purlin. The seat lies on the support and the heel stops the rafter sliding.

Field	Unit	Range or options	Default	What it changes
Point (x)	mm	from 0	1500	The tip of the V, along the part.
Depth	mm	from 1	30	How deep the notch goes.
Seat angle	°	1 to 89	35	Angle of the seat, the face that rests on the support.
Heel angle	°	91 to 179	Square to seat
Face		Top, Bottom, Front, Back	Bottom	The side of the part the processing is on.

Default: what Add fills in on a 3000 mm part of 120 x 120 mm.

Select the part in the Parts list.
Under Extra processings, click Add.
Type birdsmouth in the search field and pick Birdsmouth.
Set Face and Point (x), the tip of the V along the part.
Set Depth and Seat angle. Set Heel angle only if the heel is not square.
Check that the part shows a green check. If not, open the Issues tab.

A file that the app writes is not a check by your machine. See Export for what each format is for.