Big sanding blocks

I make these big sanding blocks out of scrap mdf by cutting the pieces just big enough to hold a half sheet of sandpaper glued to it. I use 3M Spray adhesive to hold it on. Works like a champ, spray both the paper and the mdf, let dry then wrap the paper around three sides of the block. They come in real handy for all kinds of stuff, like sanding the little nubs off these tiny pieces that like to fly out of the saw if you don't use the backer in the next post.