The sign for "exact" uses "closed X" hands (as if holding a needle
between your thumb and index finger). The top hand makes a circle in the air, then
moves down to the bottom hand. The tips of the dominant index finger and thumb make contact with
(or come very close to)
the tips of the non-dominant index finger and thumb. The left hand uses the same
handshape as the right hand. The front of the knuckles generally make
contact when you do this sign quickly.
Think of threading a needle. You have to line up the thread exactly.
The above sign for EXACT can also mean "perfect."
Quite a few signers choose to initialize this sign with a "P" to mean
The tips of the middle fingers don't actually have to touch though (because
it is hard to do this sign perfectly - heh).