A small roller 50 is mounted from the cross bar 51 of the U shaped {HEAD ~ guide bar} 48, with the bracket 52 mounted on the cross bar 51, L shaped stem extending from the bracket 52 downwardly adjacent the leg 49 of the U shaped guide bar 48, and with the roller 50 rotatably mounted on {TAIL ~ leg} 55 of the L shaped stem 54 
A small roller 50 is mounted from the cross bar 51 of the U shaped { HEAD ~ guide bar } 48 , with the bracket 52 mounted on the cross bar 51 , L shaped stem extending from the bracket 52 downwardly adjacent the leg 49 of the U shaped guide bar 48 , and with the roller 50 rotatably mounted on { TAIL ~ leg } 55 of the L shaped stem 54
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