49 Brilliant Garage Organization Tips, Ideas and DIY Projects - Page 31 of 49 - DIY & Crafts. This looks like Bouillon Cube jar lids screwed to the board, so jar part can screw onto the lid. I've also seen done with baby food jars.
To hold a lot of pliers, it's easiest to just hook them onto the edge of a piece of wood. The piece of wood in this holder is tapered towards the top edge, so that it doesn't force the handles too far apart