To make round corners in woodworking, you can use common items. Establish your cut-line with something in your shop or garage that closely matches the corner you want to cut. You might hear a woodworker refer to a "pop can" a "putty can" or a "masking tape" radius. The craftsman has used the bottom of one of these items to trace the radius from the item onto the wood. There are all kinds of radius corners around you. Pick one up the next time you need to make a corner.
Select a putty can, pop can or roll of masking tape from your supplies.
Lay the panel door out on a flat surface. Slide the can or tape roll into the corner until the bottom radius of the can touches both sides of the corner. Trace the circle from the bottom of the can onto the door with a pencil. Do all four corners.
Cut out all the pencil tracings of the can bottom with a band saw, but leave the pencil line so that you can still see it.
Sand the corners down to the pencil line on a stationary sander, rounding and blending each one as you hold the panel with both hands.
Sand the edges with an orbital hand sander using 100-grit sandpaper.
For small radius corners, use coins such as quarters, nickles or even dimes. The example here is for a type of cabinet door that has rounded corners. Use the same procedure to cut any round corners such as a countertop, the rounded corner of a wooden chair where the armrest meets the leg, round picture frame corners, window transoms or anywhere you need a rounded wooden corner.
Always wear safety glasses when working with wood.