A thread catcher is a great way to use up scraps of material. If you want your thread catcher to be washable, make it out of cotton, such as leftovers from quilt projects.
But you could also make the thread catcher out of satin, wool, or other non-washable materials. You also need some kind of weighty filler for the counterweight that holds the threadcatcher in place on your sewing machine.
Most patterns call for sand, but you could also use lead shot, fishing weights or glass beads. You'll also need interfacing or some other stiffening material for the straps, and matching or coordinating sewing thread.
You can decorate your thread catcher with buttons, rickrack or ribbon.
The thread catcher consists of a 5-inch square pillow filled with sand, joined to a lined, square-bottomed fabric bag by straps. The sand-filled pillow doubles as a counterweight to hold the thread catcher in place, and as a handy pin-cushion The thread catcher bag can be any size you want, but a convenient size is 6 inches by 8 inches by 8 inches.
The bag is lined so that when you empty it, you can pull the lining out and shake it over a trash can to make it easier to remove all the loose pieces of thread.
Sew the weight/pincushion and fill it with sand or other weighting material and sew it closed. If you're using sand, it's a good idea to make an inner pillow of tightly woven fabric and stuff this inside your outer, decorative pillow, to help prevent leaks.
Sew your thread-catcher bag, but leave the top unhemmed. Sew an identical bag our of your lining material and turn the lining bag wrong side out.
Fit the lining into the bag and fold the tops of both bags over in a cuff, as if you were folding down the top of a paper grocery bag. Top-stitch the cuff in place Attach the thread-catcher bag to the weight/pincushion with straps.
Some people use Velcro so that the bag and the pillow can be separated, while others stitch everything together.