-- Last Updated: Nov-03-12 4:12 PM EST --
I drill holes in thwarts and seat frames a little over sized, for example, a 1/4" diameter hole if you are using #10 stainless steel machine screws, then get varnish into the holes.
If the holes are drilled just big enough for the hardware the varnish will make the holes a little too tight and you tend to scrape all the varnish off when the bolts go through.