Abstract: A concrete forming panel system having at least two rectangular panels wherein each panel has a pair of spaced apart sidewalls. Each panel has at least one opening along each sidewall and the panels are adapted to be positioned in a side-by-side relationship so that one sidewall of each panel abuts against the sidewall of the adjacent side panel and, upon doing so, the opening in one sidewall of the first panel registers with the opening in the abutting sidewall of its adjacent side panel. An elongated pin is slidably mounted to each panel and movable between an extended position in which the pin extends through registering openings on adjacent panels, and a retracted position in which the wall pin is retracted from said registering openings. A latch is pivotally mounted to the pin so that, with the wall pin in its extended position, the latch pin extends through a transverse opening in the pin to lock the sidewalls of the adjacent panels together against relative movement.