Hello,
Countersunk heads should be fine.
And the pre-drilled screw holes on these plates are 5mm in diameter, except for the one in the middle, which measure 8mm in diameter.
The length of screw you should use will depend on your installation requirements (i.e the thickness of the material these are being drilled into).
Thanks for using Q&A
Answered by: DGIFF
Date published: 2020-12-15