between the lever 422 and the frame 110 an intermediate member 424 is located between the deck 106 and the first portion 427 of the lever 422 the intermediate member 424 is substantially rigid and movable along the lever 422 because the second portion 426 of the lever 422 is pivotally connected to the support member 411 the first portion 427 of the lever 422 will be rotated when the deck 106 suffers some downward displacement the resilient member 421 is elastically compressed to provide resistance to the displacement of the deck 106 as mentioned previously the position of the intermediate member 424 could be adjusted along the lever 422 to modify the resistance to displacement of the deck 106 in this embodiment there are other ways to modify the resistance to displacement of the deck 106 it would also be possible to horizontally move the position of the resilient member 421 along the lever 422 when the resilient member 421 is positioned closer to the second portion 426 of the lever 422 the resistance to the deck 106 would be decreased and the cushion effect would be soft the cushion effect would be hard when the resilient member 421 is positioned farther away from the.