An adjustable form, for use in casting cementitious material on a preformed footing structure. The form having a frame, a pair of parallel-spaced vertical sidewalls, and at least one vertically disposed oblong aperture within one sidewall. The vertically disposed oblong aperture allows for placement of a connecting pin through the oblong aperture so as to connect one form with respect to a second form offset relative to the second form. Thus, accommodating variations in the preformed footing with one form being.