The plug-through sleeve (5) extends away from the threaded leg (2) and has an effective overall height which is greater than the thickness of an add-on part (14).

A fastening clamp for connecting a carrier part (13) and an add-on part (14) has a plug-through leg (1), with a plug-through sleeve (5), and a threaded leg (2), which is connected to a thread unit (10).

The plug-through sleeve (5) extends away from the threaded leg (2) and has an effective overall height which is greater than the thickness of an add-on part (14).

A fastening clamp for connecting a carrier part (13) and an add-on part (14) has a plug-through leg (1), with a plug-through sleeve (5), and a threaded leg (2), which is connected to a thread unit (10).

Each longitudinal groove (6, 7) is thus alternatingly through-going and alternatingly not through-going.

The midsole (10) is formed with a vertical through-groove (11), a horizontal through-groove (11), or a cross through-groove (11).

The extramedullary plate has a first through opening and a second through opening.

The socket defines a socket radius.

Each of the first through regions (11) surrounds a rectangular conductive second through region (12) formed therein.

A socket (40) comprises a socket body (41) and a socket holder (50).

The socket includes a socket opening, the socket opening composed of the first material.

In addition to the ball-and-socket connection, elements may connect in a socket-to-body connection, or a number of different types of socket-to-socket connections.

The socket insert is receivable within the socket for electrically connecting the socket insert to the socket.

The socket includes a socket interior, the socket interior composed of the second material.

The magnetic attracting socket has socket contacts(6) and socket magnets (2) fixed on a panel of a socket casing (4).