noun, noun or participle which takes 'suru'
halving joint; scarf joint
A woodworking joint where two pieces are notched so they fit flush. 相欠き is the standard term; 合欠き is a variant spelling.
この棚は相欠きで組まれている。
This shelf is assembled with halving joints.
木材を相欠きにして接合する。
Join the timbers by halving them together.