miltski

my passenger seat bold(door side front) is loose, when i tried to tighten it up it appears that it has been threaded, so i look underneath thinking i'll just nut and bolt it, but it doesn't appear to go all the way through the floor.
so do i try and retap the thread, or screw the bold back in and glue it(don't wan to do this) or drill right through the floor and do nut and bolt?
or am i missing something.
the seat is not loose on any other fixing, but I would like four to hold the seat as tight and unmoovable as poss
ideas anyone?