Phidgets TSL4123_0 Cube plug PG40
This holder is used to connect 3 extruded profiles to form a 3D corner, e.g. the top of a cube. You need to use an M14 tap to drill out the end of the profiles, into which you insert the supplied reducer. Then simply screw the bracket on with an M8x20 screw. Ideally, use a screw with the head according to DIN 7991, but it's not really that important.
Manufacturer Datasheet Phidgets TSL4123_0 (3.92.4040.02)