PURPOSE: To aim at the promotion of lightweightiness in thinning the thickness of a mold as a whole, making the framing work and carrying so as to be easily performed, and also to keep an interval between two molds at a constant space accurately and positively.

CONSTITUTION: Two forms 1 and 1 being opposed to each other consists of a wire net 3 and also is made up of a plastic sheet 4 to be addedly installed on an inner surface of this wire net 3. These forms 1 and 1 lined with the plastic sheet 4 onto the wire net 3 and an interval keeping member 2 keeping an interval between these forms 1 and 1 constant both serve as the specified length interval keeping part, and a pair of reinforcement fitting parts 7a and 7a to be fitted with reinforcing bars are formed in both the end parts. In addition, two form contact parts 8 and 8 with flat contact surfaces 8a orthogonal with the longitudinal direction of the interval keeping member 2 are formed at both ends of the interval keeping member 2. Moreover, an engaged groove being engaged with a rib is formed in the contact surface 8a.