The rules for bolas in Sword and Fist are in the opinions of some philestines, overpowered.
They basically function as a medium throwing weapon that does 1d4 damage on a successful hit. And I believe the throw is touch attack, could be wrong, but anyways. If you hit with a bola the creature falls prone, and must then roll a grapple check versus your attack score or be grappled ala the rules for the net.
It's an exotic weapon proficiency, naturally, but super useful against anything that walks.