To do this sign correctly you have to smack your dominant hand down onto your non-dominant hand. The motion is so fast and forceful that the dominant hand bounces back up a bit.
Memory aid: Think of your dominant hand as representing some sort of document or picture that proves you are "right." Throw the picture onto the table in front of you as if confronting someone with the "proof" of whatever it is you are trying to prove.
PROOF:
If you mean PROOF as in "the act of testing or making trial of anything" one way to express that concept is use the sign TEST or EXPERIMENT.
If you mean PROOF as in "child proof / baby proof" one way to express that is to sign BABY + fingerspell PROOF or sign CHILD + fingerspell PROOF.
The sign PROOF is sometimes used in conjunction with other signs to create a new (but similar) meaning.
AUTHENTICATE / INVESTIGATE + PROOF:
AUTHENTICATE / WITNESS / see-with-own-eye PROOF:
EVIDENCE-[double-movement-version/initialized-version-of-PROOF] / ECONOMY / economic:
Notes:
See: ARGUE
Notes: