Originally Posted by
miriam
Cams or disks change the stitch pattern. They are usually oddly shaped. You put one on the place the machine has for them. Some 'readers' ride along the outside of the cam or disk and the machine makes a patterned stitch. You do not need this unless you are doing decorative stitching. A simple straight stitch will do an awful lot. Maybe you can try searching sewing machine disk or sewing machine cam and then the model sewing machine you have. Like 'Singer sewing machine 503 disks' and see if you have better search results.
I think I got it! It is a template that attachs to the machine, but removable like a spool of thread would be, that causes the needle to move in a way to make things like waves, or blocks or initials. It would be the difference between using a cookie cutter and pencil on cardboard or using the computer to make a design. Those sound like fun things to use. I will have to remember them.