Abstract: Hole forming devices have to be engaged between forms prior to pouring concrete. They are adapted to expand when in position to engage the inner faces of the forms thus holding them in position. The jack is a telescopic rod or tube having a heavy expansion spring surrounding same and normally urging the two portions of the hole forming device outwardly, but being held in the compressed or "set" position by means of a pin engaging through the two portions of the telescopic rod or tube. In one embodiment, when the pin is pulled, the sharpened ends of the rod or tube move away from one another, pierce the end caps of the forming device and engage the faces of the forms and at the same time move the end portions of the forming device outwardly into contact with the inner faces of the forms. In another embodiment, the ends of the rod or tube move outwardly and engage end pieces which in turn move outwardly and urge cylindrical saw-tooth end caps into contact with the inner faces of the walls of the form.

Abstract: This is a device for forming vents or bores in concrete floors. A cylindrical base portion is secured to the surface upon which the concrete is to be poured and a rigid foam cylindrical portion is pushed downwardly into the base whereupon an upper cylindrical guard portion may be pushed over the upper end of the cylindrical core. Both the base and the guard portion are provided with inwardly projecting lugs which hold the cylindrical core into the base and hold the guard portion of the upper end of the cylindrical core. An ignitor cord harness extends around the cylindrical core which, when ignited, melts this core. The concrete floor is poured with the guard portion projecting above the floor level and after the concrete has set, the ignitor harness can be ignited thus melting and charring the core thus leaving a smooth cylindrical bore through the concrete floor.

Abstract: This is a device for forming vents or bores in concrete walls or floors. Basically, it consists of a sleeve containing a semi-rigid thermoplastic material or the like and means incorporated therein which, when ignited, either melt or burn out the core. These are inserted within the forms or on the floor surface prior to the pouring of concrete or the like and may remain in place in the finished wall or floor until they are required. The core includes a pair of semi-rigid thermoplastic sections urged outwardly from one another by a spring so that they engage the wall forms. The preferred embodiment includes ratchetted wall form engaging strips secured between each end cap and a detachable tool for urging the strips outwardly thus forcing or jacking the end caps into engagement with the wall forms when the spring is not strong enough for this purpose.