Electric Terminal Blocks
The wire may be wrapped directly under the head of a screw, may be held by a metal plate forced against the wire by a screw, or may be held by what is, in effect, a set screw in the side of a metal tube. The wire may be directly stripped of insulation and inserted under the head of a screw or into the terminal. Otherwise, it may be either inserted first into a ferrule, which is then inserted into the terminal, or else attached to a connecting lug. which is then fixed under the screw head.
Depending on the design, a flat-blade screwdriver, a cross-blade screwdriver, hex key, Trox key, or other tool may be required to properly tighten the connection for reliable operation.