But you do so at the expense of floor space.
How to build a attic knee wall.
Nail down the sole plate the bottom of the wall in three or four places into the attic floor.
Install insulation without misalignments compressions gaps or voids in all knee wall cavities.
Mark the line that the angle forms along your 2x4.
Face the knee wall with the appropriate size of drywall.
Ideally confirm that the marks are level with a laser level if you have one and revise if.
The higher the knee wall the greater the amount of useful wall space you create in your finished attic.
Step 1 measure the attic to build your walls to the correct length measure the angle of the rafter by laying a piece of 2x4 inch lumber against the side of the rafter in a vertical position.
Install an air barrier on the exterior of attic knee wall insulation and to block open floor joist cavities under attic knee walls.
Install a top and bottom plate or blocking at the top and bottom of all knee wall cavities.
Do the same thing for the angled top of your knee wall nailing it into the rafters in three or four places.
Push the knee wall firmly into place.