My Dad and I went to Home Depot and bought a 1x4 board and I measured 7 1/2". My Dad cut it and I held onto it Then I found some 2" hole straps in his shop. I found bolts in some boxes. I drilled some holes in it and popped the screw into the holes. I spray painted it 2 times and let it dry for the day. Then I put the sandpaper on it.I slide the sand blocks against each other and in the middle is the sandpaper to make the noise. You move the blocks in the upright position back and forth.
I slide them together lightly to make a lower sound. If I push them hard I get a louder sound. The timbre of the instrument is rough. You can change the dynamics by rubbing the sand blocks together soft or hard.