I have been using a crosscut sled for a while now and the one thing that's not too good about it is the difficulty of dust extraction. Having thought about it for a while I decided that a box that ran the length of the sled with a hole in it for the hose would be a good solution. I initially thought that I would make it out of perspex and use some brush draught excluders on the bottom so I could still have a seal with a piece of wood in place to cut too. I went to the local DIY store and would have had to spend around £40 for the bits I needed, I thought this was a bit much so i came home and had another think. The following design was built from bits and pieces I had around the house, its a bit rough but it does work so I'm happy

Materials
2 CD boxes
Offcuts of wood
Instant grab adhesive
Foam - I got mine from an old memory foam pillow!

Tools
Saw
Drill press / drill
Knife
Ruler
Pliers

Step 1: Harvest Your CD Cases

I wanted to have a clear top just so I could see what was going on while sawing so was looking around my house for suitable materials and saw some CD's and thought that they would probably do.
It was pretty easy to cut the cases to size, each CD case will give you two panels one from the front and one from the back. First I snapped off the edges of the case with a pair of pliers so the plastic would lay flat. I then scored the plastic with a knife and ruler a couple of times so I could get all the pieces a nice uniform size, and then snapped the edge off with my hands. You should wear safety goggles or a face visor for this as small bit can fly off occasionally. You just need to trim the other sides and repeat on the other CD cases until you have enough to cover the length of your crosscut sled.

Step 2: Wooden Frame

For the wooden frame the one thing you need to do is make sure that nothing gets in the way of the fence nearest you as this is your reference edge. I decided that I would cut a slots in the frame on the front edge that fits over the fence and the use a couple of bits of timber on the far fence to guide the end of the frame (the pics make this clear!) The depth of the slots depends on your fence height and the maximum depth of cut you do with your sled, what you are aiming for is to leave a gap at the bottom that will fit the pieces of wood you are going to cut most of the time. I determined this dimension by looking at the height of the saw cut in the front fence as this was obviously the deepest cut I had made on this sled.
After determining all your dimensions cut an appropriate sized slot in two pieces of timber and cut them to the correct length so they fit over the front fence and stop just shy of the front face of the back fence. Next I glued and nailed on end panel and some small pieces of wood between the two pieces to make the frame. I spaced these so they would coincide with the ends of the plastic panels. After that I glued and nailed some more bits to the back fence of the sled to make a guide for the frame.

Step 3: Add the Plastic Roof

Now the frame is complete you need to glue the plastic CD panels to the top of the frame. I used some instant grab adhesive I already had open to do this. I then measured the diameter of my shop vac hose and cut a hole in the CD case using a Fostner bit and drill press. After doing this I tested the fit and thought that the plastic was too thin and bendy to make it a robust solution so I got another wood offcut and cut a hole in this and attached it to the frame above the other hole. I placed the hole fairly close to the front fence as most of my cuts are on smallish bits of wood and would mainly be in this area.

Step 4: Add a Skirt and Finished

Having initially thought of using door brushes as a skirt and deciding they cost too much I was looking around for alternatives. I had thought that I would have had some foam from computer parts packaging that i could use, but couldn't find any. I then came across a memory foam pillow I got free with a mattress which I had never used which sealed the fate of the pillow! I used my knife to cut two slices of foam and glued them on to the frame with the instant grab adhesive. This didn't glue too well so ended up using super glue instead. I did place it to high at first and had to rip it off and refit which left the side with the black adhesive on it which doesn't look too good but it is only for dust extraction.

I did a couple of test cuts and it worked pretty well definitely a vast improvement on loads of dust flying on to my head and probably much better for the old lungs too! Nice.