Western horseback riders began using chaps to protect their trousers from snags from plants and cattle horns. In the northern ranching areas, chaps wrap around the entire leg and are used to retain heat. Chaps are now popular in horseback and motorcycle riding. Chaps can be expensive to purchase, but you can make a pair out of your old denim trousers.
Choose a pair of jeans. Choose ones that are loose, as you will be wearing the chaps over your other clothes. Also choose jeans that are thick and durable if you are going to wear these chaps when riding a motorcycle or horse.
Determine what style of chaps you would like to make and mark out the appropriate pattern. If you would like them to simply cover your legs and have an open seat and back, mark out a line along the side seam of the jeans on either leg. Also mark out a line on the inner seam. Mark the seat by making a straight line under the back of the waistband from one side seam to the other.
Use a seam ripper to take apart the entire seam on the inner and outer sides of each leg. Stop ripping the seams when you get to the waistband. At the waistband, use the seam ripper to rip out the entire back of the trousers from the waistband. This should release the entire back of the trousers.
Hem the new edges of the chaps by folding the denim over ¼ inch so that the raw edge is on the inside of the trousers. Sew the hem shut with a straight stitch 1/8 inch from the edge of the fold. This will prevent fraying. Hem the outside and inside of each leg. The waistband should have a hem intact. If it does not, hem the bottom of the back of the waistband.
Preserve the leftover scraps of denim to make straps to hold the chaps to your leg. Cut two 2 ½ inch wide strips at the widest part of the scraps. Hem each strap along the long edges by folding the denim over ¼ inch and sewing a straight stitch 1/8 inch from the edge.
Put the chaps on and pin the straps to the back of your chaps around the lower part of your thigh or wherever is comfortable and secure. Pin the straps in place and gently remove the chaps. Use a straight stitch to sew the straps to the back of the chaps and cut off the excess strap at each end.
Embellish your chaps with leather fringe along the outer edge.
Leather chaps will protect you better than denim chaps and are recommended for motorcycle riders.