Product review (3 stars): Turns out that I didn't need it after all.
No directions were included.  I had to search online the installation procedure.  It turns out that you have to snap the two pieces apart and use the second piece as a spacer for the right hand hinge.  However, when I went to install this hinge lock, I discovered that I didn't need it.  At some point, Engel had made a change to the right hand hinge so that the pin points inward, making it impossible for the lid to come off.