Abstract: A form having a selectively adjustable curvilinear surface is provided by securing a flexible connection plate to the rear side of a flexible form panel and clamping the plate to a rigid waler to lock the panel in the desired curvilinear configuration. The connection plate is of angle-shaped cross-sectional configuration with a first flexible leg portion secured in parallel relationship to the flexible panel and a second leg portion disposed in normal relationship to the first portion. The second portion is excised at spaced intervals to accommodate flexing of the first portion and selectively clamped to the rigid waler to lock the first portion against flexing.