The importance of a good sled is underated. I'm not talking just about the snow kind. Though experience shows it's true there too.
Woodworkers use a "sled" to hold a workpiece while pushing it through a saw. This gives us a safe way to hold the piece while keeping our hands far away from the blade.
One of the first tools I made after getting into woodworking was a small crosscut sled. It has a "runner" on the bottom that fits in a slot on the table saw, and you push it over the saw blade to cross-cut a board at an exact 90° angle. (I mostly use a miter saw for these types of cuts now.)
*Picture is not my actual sled. Mine is in storage and I didn't want to dig it out just for this blog post. Credit to woodgears.ca linked below for this photo.
Another more complicated sled I made is for cutting slots on the corner of joined boards at a 45° angle.
This is how I made the slots for the splines on the corners of this picture frame.
Gluing a different piece of wood into the joint with the grain running across the miter strengthens the corner and adds a bit of decoration.
Here's a sled with a special angle to make safe, consistent cuts on the bandsaw for the pyramids that decorate the doors I'm making.
There's even a fancy sled big enough to trim a heavy seven-foot tall door.
Here are some links for instructional videos on making a table saw crosscut sled which I learned from.
And in case you wondered, that "kid" flying off the Philly Art Museum steps on a sled is me!