Reply by dbray45

Back the screws out and make sure they are not snapped off. Since this is a seat, drive 2 nails, one on each end in a downward angle. Take out the screws and using the next larger size, same length and drive them by hand with a drop of glue on each screw. Here is the reason -

The nails have a much higher shear strength than screws but loosen over time. Screws hold tighter.
Drill driven screws either snap off or drill out the wood – so you need to hand tighten. If, after you run your pilot holes, slightly counter sink one of the holes on a side that they are together, the two pieces will be a lot tighter together.

Hope this helps

-- David in Damascus, MD