a. The instruments that are placed on the Mayo tray are those that will be used for making and opening the initial incision. These are the instruments that the surgeon will use at the beginning of the procedure.

b. For each basic procedure, a definite class of instruments of suitable size, shape, strength, and function is required. For example: knives and scissors are for cutting or dissecting; tissue forceps are for grasping and holding; hemostatic forceps and clamps are for clamping and occluding (closure); retractors are for exposing; needle holders are for suturing; and sponges are for absorbing fluid and blood.

Figure 3-22 illustrates a Mayo stand with instruments prior to surgery. The scrub arranges the instruments on the Mayo tray for the initial incision. He must not overload the tray initially since additional supplies and instruments can be added to the Mayo tray as the operation progresses. Note how the instruments are placed on the rolled towel in Figure 3-22.