Abstract: A fastener kit for securing flexible sheet materials such as polyethelene film to a structure to provide greenhouse coverings, wind screens and the like. The kit comprises an elongate channel member securable to the structure as with screws, an elongate lock member which can be forced into the channel member with sheet materials secured therebetween, and an elongate clip member which can be used to secure second material between the clip and lock members. The clip member is formed of a rigid material which can be flexed to place two longitudinal gripping portions of the clip member into gripping engagement with corresponding surface portions of the lock and channel members, or flexed to remove the clip member. The arrangement permits the second sheet material to be secured to or removed from the structure without requiring total disassembly of the kit members and removal of the first sheet material.