Everybody hates sanding, right? I don't mind it so much myself, but certainly some sanding jobs are more tedious than others. Here's a tool that can bullnose the edge of a shelf in short order, if that's something you ever needed to do.
It's simply two notches cut into a 1" x 2" with a relief cut to allow the sandpaper to give. The strip of sandpaper is reinforced with strapping tape and wraps around two keys that fit into the notches. This arrangement works best when the sandpaper is stretched as tight as possible.

The blank actually measures 3/4" x 1 1/2" x 15".

I'm leaving 3" for the keys because I'll be using a block plane to fit them, and it's easier to plane a 3" piece than two individual keys.

Supplies

For this project you will need:

Rough grit sandpaper (60 or 80)
Strapping tape
3/4" x 1 1/2" x 15" blank
Hand saw
Coping saw or chisel
block plane (optional)
Pencil
Ruler
Square
Knife

Step 1: Layout and Cut the Notches

I often prefer to work off a center point so I'll make a mark at 12", find the center of the bow, and measure 4 1/16" off the center each way. These marks represent the inside walls of the notches. I'll lay out 1/2" for each notch and then score all my cuts, including one cut in the center which will serve as a relief cut when I'm shaping the handle.

I used a marking gauge set for 1/2" to define the depth of the notches.

Step 2: Make the Keys

From the 3" piece, I split 1/2" off one edge. It will have to be planed or sanded to a fairly loose fit.

Next, I cut a shallow kerf in one edge, no deeper than 1/8". This tiny groove will receive the end of the sandpaper.

Then, I cut 2 pieces about 1" to serve as the keys.

Step 3: Prepare the Sandpaper

The secret weapon here is Strapping Tape. Reinforce the back of the sandpaper with the tape, but don't extend the tape all the way to the ends. Leave about 3/4 of an inch untaped. The back of the tape is slippery and the sandpaper will hold better if it can grip the key somewhere. It's best if the tape goes just around the first corner of the key.

Step 4: Test the Fit

The moment of truth.

No use in shaping the handle if it isn't going to work.

Step 5: Shape the Handle

I used a roll of tape to mark the curves on the ends.

For the long curve, I clamped scraps to the blank and used them to bend my ruler, leaving the handle at least 3/4" thick.

Step 6: Finish It

Once I know it's going to work, I'll cut out the curves, sand it, and finish it. If you don't have a coping saw, a chisel will do the job just as well. The relief cut in the center makes cutting the long curve with the coping saw easier, but it's critical if you are using a chisel.

This is one of those tools you didn't know you needed until you have one. You may be surprised how often you find your self reaching for it. Happy sanding!