The older bows used a flat shelf and the newer bows use a curved shelf, that way the arrow is only on a small part of the shelf and arrow flight is not effected as much. A lot of guys use a wood match under the arrow rest and on the flat riser and that way the arrow is not on the entire rest. For the rest you can use stiff part of velcro and cut it to shape so it covers the bottom and a portion of the inside of the window. You can also get calf hair rests ready made from the mail order houses if their is not a sop in your area