Exercise sheets are used during riding, to keep certain muscles of the horse warm or to protect it from the rain. Sheets can be made from warm breathable material such as wool, or from waterproof synthetic fabric. Smaller sheets are fitted behind the saddle to cover only the hindquarters, larger sheets can be fitted under or around the saddle, where they also cover the withers and part of the shoulder. Exercise sheets may also be attached with a surcingle and breast strap to be used on horses which are being exercised in-hand.