DUCTFAB Button Punch Snap Lock (BPSL) Seam Roll Former greatly simplifies ductwork assembly. The male seam is a button, the female seam is a lock and these snap together for a flush corner.

Female locks formed on the inboard side and button punched right angle flanges on outboard rolls on a nine forming station machine.  

This is a more sophisticated joint than the Pittsburgh lock, requiring less labour. 

When used in conjunction with the double-headed flanging machine, this makes possible the forming of round bends. 

The machine is capable of forming a maximum of 20 swg (1.00mm).