Trip
From NsdWiki
Occasionally you want to pull the rug out from under an enemy. Tripping an opponent in combat is just an opposed roll.
The attacking character will roll D10 + Agility + Muscle + Weapon skill ranks + the weapon's trip bonus.
The defending character will roll D10 + Agility + Dodge + Hold + Muscle.
If the attacker's result is higher than the defender's result, the defender is tripped. No damage is incurred by a trip.
When a character is tripped, he or she has been thrown to the ground. In game terms this means the character takes a -4 penalty to any Defense Rolls.