The Occupational Safety and Health Administration (OSHA) regulates that the handrail for a staircase should be able to support 90.7 Kilogram and must be 36 inches above the stairs. When you install a handrail, you need to cut it to maintain the necessary height the entire length of the stair's run. The angles cut into the handrail are necessary to create a finished and flat surface at the top of the stairs, and a finished, rather than blunt appearance at the stair's foot.
Measure the length of the run of the stairs -- from the front edge of the top step to the front edge of the bottom step. Add two feet to this measurement and use this to determine the amount of handrail material you will need to purchase.
Cut a 45 degree angle on the one end of the handrail. Make sure you cut the bottom of the handrail, angled toward the finished top.
Rest the angled end of the handrail on the floor at the foot of the stairs. Use a pencil to mark the point at which the front edge of the stair hits the rail.
Cut the handrail at the point you marked in Step 3 at a 16 degree angle. Make sure you cut from the unfinished bottom and angle it toward the finished top.
Cut a 45 degree angle on one end of the short of the handrail piece. Try to fit the short handrail piece to the 16 degree angle and determine whether it makes a 45 degree angle. Cut more from the smaller piece, if necessary, until it fits together as it should.