i think you're talking about the best grab ever... the lui kang.
to execute, simply extend one leg fully, and tuck the other leg up, grabbing with the same hand under the boot.. let out a vicious battle-cry, and you have done a lui kang
the liu kang is the best grab ever. invented by the likes of mike nick back in the snowblading days. youtube mike nick skiboarding. take a trip back into history my friend