the simple over-centre catch...
$7 each from the local disposal store



the 25x50 tube that the catch is fixed to also doubles as a stiffener for the boxes wall, the only tricky bit was the 'hook' that I put on the lid.... I riveted them from the inside and then belted the rivets down flat so they were a flush finish inside and outside the lid, that's why the 'hook' rivets look a tad odd, the bit we normally see is on the inside of the lid



EDIT:
Oh yeah ..........

AND ITS LOCKABLE
that will keep them sticky beaked ankle biters out