Location-based attack against leg(s) at -2 versus target's Parry
If successful, defender opposes the attack roll (including the -2) with an Agility roll
e.g., Johnny attempts to sweeps Daniel's leg. He rolls D8 fighting + wild D6, -2 for the leg target: total roll 8
Target (Daniel) has Parry 6, so he is hit. Roll applicable damage (which might eliminate the need for the follow up roll, or inflict a wound that'd make the Agility roll harder.)
Daniel has Agility d8. He attempts to roll a 6 on that d8 + d6 (wild) but only gets a 5.
Bam. Flat on his back.