along the panel an alternative lock structure is shown schematically in fig1 in which the top lock and channel structure formed by the edge of the panel being folded over top lock 52 u2032 has a dog leg configuration with a free edge of the panel material being disposed so as to hook onto a bottom lock upward leg a nail channel 66 u2032 is formed above the top lock with the upper face 58 in opposition to the channel base 68 in this manner corresponding nail slots are punched in the channel base 68 and upper face 58 through both thicknesses of material contrary to the prior art double thickness nail hems the configuration shown in fig1 would have increased nail holding capability since the nail head or staple crossbar would be spaced away from the nail slots to eliminate stress concentrations while the embodiments described herein are siding panels with a top lock and a bottom lock which extend horizontally along a wall it is contemplated to be within the scope of the invention to apply the improved nailing channel to any attachment area of building panels that may be differently oriented when installed broadly the lock structure comprises first and second edge structures and a nailing area located somewhere between the edge structures as is common in the industry the siding panels described herein can be composed of a variety of plastic materials preferably the panels are composed primarily of pvc resins the capstock or exterior layer is formulated to have a good appearance and to be weather wear and impact resistant the substrate or interior layer is formulated primarily for stiffness and strength nevertheless other constructions including only one material or more than two materials could be used to form the layers or plies of.