A sai is a metal spike flanked by a pair of prongs used to trap an enemy’s weapon. Though pointed, a sai is not usually used for stabbing. Instead, it is used primarily to bludgeon foes, punching with the hilt, or else to catch and disarm weapons between its tines. Sais are often wielded in pairs.
When wielding a sai, you get a +2 bonus on combat maneuver checks to sunder an enemy’s weapon.
Pathfinder RPG Core Rulebook. Copyright 2009, Paizo Publishing, LLC; Author: Jason Bulmahn, based on material by Jonathan Tweet, Monte Cook, and Skip Williams.
Pathfinder Roleplaying Game: Ultimate Equipment (OGL) © 2012, Paizo Publishing, LLC; Authors: Dennis Baker, Jesse Benner, Benjamin Bruck, Ross Byers, Brian J. Cortijo, Ryan Costello, Mike Ferguson, Matt Goetz, Jim Groves, Tracy Hurley, Matt James, Jonathan H. Keith, Michael Kenway, Hal MacLean, Jason Nelson, Tork Shaw, Owen KC Stephens, Russ Taylor, and numerous RPG Superstar contributors