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By a simple shift in position from vertical to horizontal, an entirely different concept in concrete formwork has been evolved. The system, called horizontal shoring, actually makes it possible for a few supporting members to carry a heavy concrete load. The system is made possible because of the unique construction of the horizontal beam- three different versions of which are currently being marketed in this country. Made of steel, each beam consists basically of two elements: a lattice section and a plate section, designed on the telescopic principle. Since the lattice sections come in two different lengths, a variety of spans are possible- up to a little over 20 feet. For spans greater than this, two plate members are needed, or, depending on the type of beam you use, a combination of one plate member with two lattice sections. Let's look in some detail at the way the system works. One type of beam features a wedge bock which can be opened and closed with a few blows of a carpenter's hammer. When the wedge lock is open, the plate section glides smoothly back and forth within the lattice member, allowing for easy adjustment to the desired span. When it is closed, the camber of the beam is automatically set. With the other two types of horizontal steel beam available, a few quick turns of a wrench will loosen up the bolt and screw plate assembly at each end of the lattice member. You can then telescope the plate members to the correct length and run the bolt back up to clamp the members firmly together.