The spring nuts, widely used for fixation of steel trough and rail from inside, can automatically locate under terms when unlocking. There is threaded flute on the back of it which can slide from the front to the back. It also can play a part of fixation.

Material: Q235; 1010; 1018; 1020; 35# steel

Dimensions:
M6 x 6 x 20 x 35, long spring      
M8 x 6 x 20 x 35, long spring      
M10 x 8 x 20 x 35, long spring
M12 x 9.5 x 20 x 35, long spring
M6 x 6 x 20 x 35 (S), short spring      
M8 x 6 x 20 x 35 (S), short spring
M10 x 8 x 20 x 35 (S), short spring
M12 x 9.5 x 20 x 35 (S), short spring
M6 x 6 x 20 x 35 (L), long spring
M8 x 6 x 20 x 35 (L), long spring      
M10 x 8 x 20 x 35 (L), long spring      
M12 x 9.5 x 20 x 35 (L), long spring  
Spring can be 30, 40, 50, 60, or 70mm long.

Packing:
Carton/pallet