prevent transverse movement of the blade spring 10 with respect to the shoe 12 the wall 32 and the projection 38 also assist in mechanically interlocking the blade spring 10 to the shoe 12 the blade spring 10 is very easy to position on the shoe 12 the symmetrical design of the blade spring 10 means the blade spring cannot be installed in the wrong orientation it is also very easy to insert the blade spring into the passageway 34 and the chamber 26 of the shoe 12 and the slots 22 are easily aligned with the wall 32 and projection 38 once the blade spring 10 is in alignment with the chamber 26 it is only necessary to advance the blade spring towards the end wall 28 to position the end of the blade spring 10 in alignment with the shoulder 40 to mechanically interlock the blade spring with the shoe 12 when the blade spring 10 is positioned in the shoe 12 as described above the blade spring wants to return to its original arcuate shape and the blade spring presses against the adjacent surface of the shoe 12 accordingly the blade spring 10 places a load on the shoe 12 and this load assists in allowing the shoe to 34 creep 34 to keep proper tension on the chain the forces exerted by the blade spring 10 on the chamber 26 and the reaction surface 41 in passageway 34 of the shoe 12 are substantially equal due to the symmetrical design of the blade spring the stresses on the blade spring.