Extruding to particular thickness on an angle I keep stumbling over this one issue when extruding/aligning studs in architectural framing models. Essentially, when I have an angled edge that I would like to extrude to make a beam of a particular thickness, I cannot figure out how to achieve that thickness while keeping the ends of the beam perfectly angled to meet the vertical walls on either side. 

The gif below is one method of approach, extruding vertically to obey the vertical side walls. Note that if I input a value (say, four inches), that value will not result in a four-inch-thick beam, since the vertical extrusion is off-axis from perpendicular with the face:



So, logically, I hit Z twice, to extrude perfectly perpendicular to the face. In this scenario, however, the ends of my beam are not vertical, and most attempts at rotating or grabbing them into verticality result in altering the beam thickness (see below):



What is the best practice to do this simply? I find myself coming across this problem way too frequently to not have an elegant method. Thanks for your time!
You can get very close by:


Setting your transform orientation to 'Normal'
Setting your snap to 'Edge', Active'
In Edit/Vertex mode, (the pair of vertices selected) Extrude in Z Z by a numerically entered depth.
Translate the new edge in Y Y until the active vertex at one end 'snaps' to the wall.


But, it's not a true snap. The move is constrained, but the snap projection isn't. You can get very close by zooming in, and eyeballing the 'bullseye' of the snap range circle. Blender's snapping system is lacking, here.

You can install and use the built-in add-on  - 'Mesh:Tiny CAD' to make a true, accurate projection of the new, extruded edge to its intersection with the wall, but only if they're part of the same object, or you construct a new edge from the wall as a guide, which is part of the same object.