The usual crosscut sled is only suitable for one blade, that is the blade that cut the original kerf in the sled after it was completed. This sled is different in that the width of the kerf slot is adjustable. It can be set down for a thin kerf blade or widened out for a dado set.
I will describe this from the point of view of someone pushing the jig through a cut. The Woodsmith Shop TV show suggested using an aluminum bar to run in the miter gauge slot. It has screws that adjust how tight the bar is in the slot. Many miter gauges use these and it appears the bars can be purchased separately. I can buy such bars for the shop smith which uses non standard sized slots. There is only one miter gauge bar on the jig but with the tightening screws that shouldn't be a problem.
The fixed base of the jig extends from the blade to the left and the bar runs in the left slot. The two fences, front and back, extend from the left side of the fixed base to several inches past the blade. The fences are sitting on top of the fixed base so where they extend past the blade they are above the table by the thickness of the fixed base.
Now there is another piece that is placed to the right of the blade. it is made of the same material as the fixed base that is as wide as the fences extend beyond the blade and longer than the fixed base, towards and away from you, by twice the thickness of the fences. Let's call this the movable base. There are two fences on the movable base as long as the movable base is wide. They are at the front and back outside of the two fences on the fixed base. There are horizontal slots cut in the two fences on the movable base that were evidently cut with a router. A knob head bolt goes through each slot into threaded inserts in the fixed fences. When the knobs are loosened the movable base can be moved left and right to adjust the width of the kerf. When they are tightened down the moveable fence stays in place.
No dimensions are given because the jig will have to be constructed to fit your saw and the size of work pieces you want to cut with it.
by Max Robinson