Square M8 nut

This M8 square nut is Schletter's article SLT-943914-008, sized to slide into the channel of a Schletter mounting rail and used together with the rail's KlickIn or KlickFit click components so it can be inserted and positioned at any point along the rail without feeding it in from the end. The square shape stops the nut turning as a bolt is tightened into it, giving a secure connection for clamps and other fittings along the rail. It is a small, low-cost fastener rather than a structural item on its own, and is normally bought in quantity alongside the matching hexagon socket screws used to complete the joint.