After a system has been adjusted, the full and synchronized  movement of the controls should be checked. When checking  the range of movement of the control surface, the controls  must be operated from the flight deck and not by moving  the control surfaces. During the checking of control surface  travel, ensure that chains, cables, etc., have not reached  the limit of their travel when the controls are against their  respective stops. Adjustable and nonadjustable stops (whichever the case  requires) are used to limit the throw-range or travel movement  of the ailerons, elevator, and rudder. Usually there are two  sets of stops for each of the three main control surfaces. One  set is located at the control surface, either in the snubber  cylinders or as structural stops; the other, at the flight deck  control. Either of these may serve as the actual limit stop.  However, those situated at the control surface usually perform  this function. The other stops do not normally contact each  other, but are adjusted to a definite clearance when the  control surface is at the full extent of its travel. These work  as override stops to prevent stretching of cables and damage  to the control system during violent maneuvers. When rigging  control systems, refer to the applicable maintenance manual  for the sequence of steps for adjusting these stops to limit the  control surface travel.  Where dual controls are installed, they must be synchronized  and function satisfactorily when operated from both positions.  Trim tabs and other tabs should be checked in a manner  similar to the main control surfaces. The tab position  indicator must be checked to see that it functions correctly.  If jackscrews are used to actuate the trim tab, check to see  that they are not extended beyond the specified limits when  the tab is in its extreme positions.  After determining that the control system functions properly  and is correctly rigged, it should be thoroughly inspected to  determine that the system is correctly assembled and operates  freely over the specified range of movement.  Whenever rigging is performed on any aircraft, it is good  practice to have a second set of eyes inspect the control  system to make certain that all turnbuckles, rod ends, and  attaching nuts and bolts are correctly safetied. As a general rule, all fasteners on an aircraft are safetied in  some manner. Safetying is defined as securing by various  means any nut, bolt, turnbuckle, etc., on the aircraft so that  vibration does not cause it to loosen during operation. Checking and Safetying the System Figure 2-91.  Double-wrap and single safety wire methods for nuts,  bolts, and snap rings. Screwheads • Double-twist method External snapring • Single-wire method Small screw in closely spaced closed  geometrical pattern • Single-twist method Single-fastener application • Double-twist method Bolt heads Castle nuts 2-54