Adjustable fastener assembly for canvas covers and the like

An adjustable fastener assembly for attaching a flexible sheet cover to an object, said fastener element comprising:

• an elongated hollow housing having a slot defined by opposed edges extending the length of said housing;
• and
• a slide enclosed within said housing with a portion thereof extending through said slot, said portion carrying fastening means engageable with a cooperating fastening element on said flexible sheet cover;
• said slide and said housing being provided with cooperating slide and housing positioning means which can be engaged and disengaged by lateral movement of a portion of said slide to lock said slide at a desired location along the length of said slot and to permit said slide to be moved along the length of said slot;
• said slide positioning means having a first engaging portion capable of engagement with a first portion of said housing positioning means to prevent longitudinal movement of said slide in only a first direction and a second engaging portion capable of engagement with a second portion of said housing positioning means to prevent longitudinal movement of said slide in only a second direction;
• said housing having a C-shaped cross section including a back wall, top and bottom plates attached to said back wall, and top and bottom edge strips attached respectively to said top and bottom plates, said edge strips defining said slot;
• and
• said slide positioning means has a generally U-shaped leaf spring having first and second ends and said housing positioning means has a corresponding notched means on said backwall, engagement of said notched means with said first and second ends preventing movement of said slide along said housing respectively in said first and second directions.