The rappel seat-From the Ranger Handbook

e. Rappel Seat.  The rappel seat  is a rope harness used in
rappelling and climbing. It can be tied for use with the left or right hand
(1). Leg straps do not cross, and are centered on buttocks and tight
(2). Leg straps form locking half hitches on rope around waist. Square knot properly
tied on right hip
(3) and finished with two overhand knots. Tails must be
even, within 6 inches
(4). Carabiner properly inserted around all ropes with
opening gate opening up and away
(5). Carabiner will not come in contact
with square knot or overhand knot. Rappel seat is tight enough not to allow
a fist to be inserted between the rappeller’s body and the harness.