I found a small, inexpensive drop-leaf table on the street, and brought it home to refinish it, intending to send it to college w/ my kid.

The leaves would fold back against the underside and stay there--or they would fold up horizontal--with only the hinges themselves.

I took the hinges off so I could strip, sand, and re-poly. But when I put them back on, now they just swing free--there's no hold in those positions. (When I got them back out to put them on, they were holding tight--I had to use a screwdriver to pry the two sides apart so I could reattach them. They worked then!)

At first I thought maybe I had too much polyurethane on the insides of the butt joint--but that wouldn't explain why they wouldn't work when the leaves were folded back.

Has anyone ever encountered hinges like these?

(They look like regular hinges, actually)

Any idea what I did wrong, or whether I can fix them? And any idea how I can fix this--in a short timeframe?