A connector that is used to join a first modular barrier to a second modular barrier. The first modular barrier has a first frame element along one side with a first slot that extends along its length. Likewise, the second modular barrier has a second frame element along one side with a second slot that extends along its length. A flexible panel joins the two modular barriers together. The flexible panel has a first side edge and an opposite and parallel second side edge. The first side edge extends into the first slot of the first frame element and the second side edge extends into the second slot of the second frame element. The first side edge and the second side edge are enlarged and lock the first side edge and the second side edge into the first slot and the second slot, respectively.

Systems for building customizable structures, without tools and without separate mechanical fasteners, as well as methods of use are described. Such structures may comprise at least two separate panels removably attached to a common panel-joiner. Such panels may be substantially planar and structural members. Such panel joiners may be substantially elongate members and structural members. Edges of the panels and complimentary-edges of the panel-joiners may be removably attached to each other by virtue of a plurality of clips running along a given edge and a complimentary plurality of clip-receivers running along the given complimentary-edge of the given panel-joiner. Such erected customizable structures, may then be used in firearm and tactical training. Such erected customizable structures may simulate various building structures, such as, but not limited to, rooms and/or hallways.

An assembly of extruded members including: an extruded housing member including one or more holes formed along at least one side thereof for entry of ends of one or more second extrusions therethrough; and at least one extruded aluminum clamping member including one or more pairs of opposed clamping portions for clamping the ends of the one or more second extrusions therebetween.