The main box latch is the trigger for the table’s entire mechanical system. When the key is turned within the right side apron, it actuates a lever releasing a bolt from the bottom of the main box. Under the tension from the drive mechanisms, the main box is propelled forward while, simultaneously, the table top slides back. Before proceeding with the mechanisms, it’s necessary to mortise in the main box latch. 

This is a bit of a delicate operation. The latch mechanism has a 90° bend where the key connects which has to be mortised behind the lower rack guide. It also has a sleeve into which the key is inserted. This needs to be contained within the apron, not protruding from it. 

After a bit of drilling, sawing, and paring things finally slide neatly into place!

Next, the long portion of the mechanism must be mortised into the floor of the carcass.