
The latch is locked closed by the pin sliding through a notch in the hinge plate of hitch itself. This type normally uses a 5/16 inch pin, but if you use a 1/4 inch pin it is small enough to slip past the ears of the notch and will not lock the latch shut. I learned that today while hitching a trailer and noticed the handle did not lock down good when the pin was installed. I was using the 1/4 inch pin that came with the trailer (used trailer). I discovered that the apparent reason for the 1/4 inch pin rather than the 5/16 was that the holes were not aligned quite right and it was nearly impossible to get the proper 5/16 pin in the latch. A quick pass with a 5/16 drill bit and the proper pin fit just fine, and the hitch locked closed as it should.