A keyhole recess for picture hanging flush to the wall.
Ref. 35/01 - No.10 & No.12 screw heads.
Not suitable for grooving applications.

Specification:
D=12.7 mm
D2=8 mm
S=4.6 mm
C=4.9 mm
OL=38.1 mm
Shank Diameter=1/4 inch