I had a need to make some controlled crosscuts on some 12" planks. This is too wide for my miter saw, so a crosscut sled was put at the top of the project list.
I browsed around the Internet looking for plans and design ideas. I decided to go with a fairly straight forward style with a base and beefy fences. The bottom base is made of 3/4 MDF and was cut to fit over the main table saw area and the extension to the left. I figured that the "long" end of the wood would be to the left, so most of the fence is also to the left.
The photo below shows the bottom of the sled. Although it is difficult to see, each of the runners is made of oak and sits in a shallow dado. I didn't want to just glue & screw the runners in place... I wanted them locked into the proper position so the glue would have less work to do. Getting the runners aligned with the miter slots on the table was the hardest part of this project.
Making the first dado was fairly easy. Just measure over from the edge and make sure it runs perpendicular to the front edge. Placing the second dado so it was exactly over the second miter slot was much harder. I am sure experienced woodworkers could have done this with ease, but it took me most of a day. There was lots of measuring and checking for square. Basically I put the loose runners in the slots, lined up the first one in the first dado, then clamped the second one to the base. This then gave me a good starting point for where the second dado should go.
Finally I glued and lag screwed on a double 2x4 for the rear fence and a single one for the front. I did not spend a lot of effort making sure the rear fence was perpendicular to the saw blade, but instead lucked out and got it pretty close.
The first use of the sled was to square up some bench legs that had been cut with a circular saw (without any guide). It worked well, but as the humidity changes, the wood runners swell and sometimes is it difficult to slide across the table saw. I just keep sanding them until it slides.