Strike Box aka Dust Box

Slip this dust box behind the strike plate on your door frame to give it a neat and clean look. This hides any imperfections in the recess and stops dust from migrating out of the wall cavity.

The Fusion 360 (F3D) file is fully parametric. The STL file is sized for my interior doors but might not fit yours. Go into Modify → Change Parameters to adjust the sizing.

Update: because of recent changes to Fusion 360 Personal licensing I'm moving everything into FreeCAD. Go into Spreadsheet → Parameters to adjust the sizing.