Abstract: Structures used for dividing, supporting, disguising and/or cladding, for example, modular wall panel systems can include frame members that can include or be in the form of a rail having a panel engaging portion with a generally planar mounting surface configured to accept at least one fastener, the panel engaging portion including first and second lateral sides on opposite sides of the generally planar mounting surface. First and second channels can include side walls extending generally parallel to the generally planar mounting surface, the first and second channels facing away from each other.