| 摘要 |
A channel member having its flanges extending at an acute angle to the web and having inturned margins on the free edges of the flanges is imbedded in plastic concrete in approximately the position of a threshold plate or other structure to be mounted, the set concrete retaining the mounting channel in fixed position by the dovetailed relation of the flanges in the concrete with the open top of the mounting channel substantially flush with the concrete to also serve as a screed guide for the plastic concrete; a plurality of spanner bars of channel shape and of a length greater than the spacing of the flanges of the mounting channel are provided with slots which extend the full distance between the free edges of the inturned margins with a square lock nut such as the type having a nylon strip in a keyway is slidably positioned in each spanner bar channel and a flat head or oval head mounting screw for the threshold extends through corresponding countersunk apertures in the threshold and threaded into the square lock nut. The spanner bars are attachable to the threshold with the screws and nuts and arranged substantially longitudinally along the threshold; the threshold is then placed in position with the spanner bars falling into the mounting channel cavity and the threshold is accurately positioned for cooperation with the door with which it is used and the machine screws are turned with a screw driver causing the spanner bars to first rotate with the lock nut until rotation of the spanner bars is stopped when the ends of the spanner bars underly the inturned margins by engagement with the flanges of the mounting channel, each spaner bar sliding on its cooperating nut to the correct position corresponding with the selected accurate position desired for the threshold and further tightening of the machine screws clamp the threshold permanently in place, the threshold plate being removable by rotating the screws in the opposite direction.
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