I was looking for a solution for making all my table saw jigs and sleds slide smoothly along the miter slots. A quick solution is to cut wooden miter bars out of scraps from around the shop, but they have to be milled precisely for a good fit. Also, wooden bars have the potential to wear down over time or shrink or swell due to changes in humidity (a problem in the Houston area) leaving you with a sloppy fit and less precision. 

 

As an alternative, at most any of your home improvement stores you can find 3/4" aluminum square tubing that fits perfectly in most 3/4" mitre slots. 

 

With a carbide tipped table saw blade you can rip the aluminum tubing right in half giving you two perfect miter bars.  Cut these to any length, pre-drill for mounting screws, and attach to the bottom of any jigs. 

 

Easy, custom fit, and inexpensive. - Tray Wright, Texas