TM 9-2320-361-34 13-3. FRAME ALINEMENT INSPECTION (Contd) NOTE Strings used for horizontal bow measurement will remain in place until procedure d, frame squareness, is completed. On frames longer than 20 ft (6 m), the two front and rear strings will be used. 5. Stretch string tightly on floor (5) between front and rear plumb bob marks (2) under each frame rail (1). Place weights on string to keep it taut or tie ends of string to jack stands. NOTE For frame rail sections with added fishplate, subtract 5/16 in. (7.94 mm) from plumb bob marks to compensate for the fishplate added to frame rail. 6. Measure distance between string and each plumb bob mark (2). If distance is more than 1/2 in. (13 mm) from bow (3), or 1/2 in. (13 mm) from bow (4), frame rails (1) are out of tolerance. NOTE If measured frame rails are out of tolerance, notify supervisor. If frame rails are verified to be out of tolerance, truck will be classified as unserviceable. c. Horizontal Bow Inspection, Frames 20 Ft (6 M) or More NOTE On trucks with a frame longer than 20 ft (6 m), the front 20 ft (6 m) of frame rail (measured from front to rear) and the rear 20 ft (6 m) of frame rail (measured from rear to front) are measured separately. This will cause an overlap in measurement. Perform procedure b for each 20 ft (6 m) section of left and right frame rails (1). 13-4