To sand coves, wrap sandpaper around small lengths of clear flexible plastic tubing. Most hardware stores carry this type of tubing. Choose a diameter smaller than the radius of the cove. Slice the tube down its length and slip one edge of the sandpaper into the slit. Then wrap the sandpaper around the tube and hold it tightly.
To take measurements inside an area like a cabinet drawer, use your measuring tape from inside edge to inside edge. Take the reading and then add on the length of the tape housing which is often stamped on the case. Another way is to use your tape along with a combination square. Position the square upside down in one corner and pull the case past the square’s blade. Select a number on the blade, and add the length of the tape.