T-slot nuts for 20mm based ALU profiles and low profile nuts.

After experimenting with various T-slot nuts this design works the best for me. The connection is rigid and sturdy even with one single corner bracket. Parts can be used with low-profile M4 or M5 nuts only and use of a washer is highly recommended - see pictures for details.

There is 15mm distance between the nut-holes in the 'double' version to fit exactly double corner brackets, I use.