Wash the towels, terry cloth or woolen sweaters. Use the hot water setting. Dry them thoroughly at a cotton heat setting.
Cut the towels, terry cloth or woolen sweaters into 3/4-inch strips. Avoid worn areas in the towels or terry cloth. Cut the sweaters in a spiral manner to get a long strip, starting at the bottom and working up toward the sleeves.
Cut the strips into 6-inch lengths.
Cut a piece of gridding the size you want your bath mat.
Knot a 6-inch fabric strip onto the gridding using a single square knot.
Thread an upholstery needle with buttonhole thread. Tie a knot in the thread end. Push the needle through the center of the knot using a thimble. Take a back stitch to anchor the thread.
Tie another strip of fabric onto the netting next to the first one. Put the needle into the knot, take a back stitch, then a cross stitch, then a back stitch. Repeat this sequence down the row of gridding.
Tie another strip of fabric onto the netting next to the first one. Put the needle into the knot, take a back stitch, then a cross stitch, then a back stitch. Repeat this sequence of knotting and stitching down the row of gridding.
End the buttonhole thread when you are within 6 inches of the end by taking two back stitches and then cutting it off close to the fabric strip. Rethread the needle and continue stitching as before.
Examine the density of the pile produced after doing several knots. Adjust the spacing as needed by skipping a space if the pile is so thick that it is hard to knot the next space. Complete the knotting and stitching and use the rug.