SeaKan wrote:
one or more of my registers are unable to be screwed in. why you ask? b/c
there is no drywall or metal to go through. what can i do about this?

Bend up some metal angle clips from scrap metal (old ductwork would be
good) and Tek screw them to the sides of the duct. Sheetmetal screws
hold the register to the clips.

R