Rebates are open sided grooves cut on the edge of a workpiece, as shown in the picture here. They are also known as rabbets. Depending on the size of the work, the woodworking technique for making the rebate varies.
Very small rebates are made using a side rebate plane tool. These have two blades, one on each edge, so that the tool can be used from right to left or left to right.
The tool allows you to trim both sides of a groove when working from only one end of the piece to accommodate the grain direction of the wood. It also includes a depth gauge which acts as a guide to maintain the base of the rebate at right angles to the wall surface.