ends or legs 112 and 114 which extend from opposite ends of the base portion and parallel to one another the base portion is covered by a protective sleeve 116 which is preferably made of plastic a slot 118 is provided in the first end 112 of the member 110 fig2 and a threaded hole is provided in the second end 114 of the member 110 the bolt 120 is preferably made of steel and has a shaft 121 which extends perpendicular to the ends 112 and 114 of the member 110 a first end 122 of the bolt 120 is provided with a head having a diameter which is greater than the diameter of the shaft 121 a second opposite end 124 of the bolt 120 is provided with external helical threads which mate with the threaded hole in the second end 114 of the member 110 the second end 124 of the bolt 120 is inserted through the slot 118 then through a hole in a first flange or tab 92 on the device 90 and then through a helical coil spring 130 a stop 140 is then rigidly secured to an intermediate portion of the shaft 121 on the bolt 120 in such a manner that the spring.