This invention is a form structure of lightweight construction so as to be readily movable during various stages of construction while providing a rigid structure operable for construction of concrete walls without warpage. More particularly, this invention is a form structure including (1) a main body of vinyl foam core having exposed surfaces covered by layers of fiberglass material and the concrete contacting surface provided with a Black Gel coat of polyester resin, (2) upright edges provided with interlocking joint members whereupon adjacent form structures can be secured to each other through the use of latch and hook assemblies; and (3) a plurality of horizontally extended ty-hole assemblies are provided for interconnecting adjacent, cooperating front and back form structures in a spaced relationship for pouring concrete or like materials therebetween.