This section is from the book "Cyclopedia Of Architecture, Carpentry, And Building", by James C. et al. Also available from Amazon: Cyclopedia Of Architecture, Carpentry And Building.
Fig. 182, Spacers for holding the bars in place in beams and girders, have been successfully used. These spacers are made of heavy sheet iron. They are fastened to the stirrups by means of the loops in the spacers. The ends of the spacers which project out to the forms of the sides of the beams, should be made blunt or rounded. This will prevent the ends of the spacers being driven into the forms when the concrete is being tamped. The number of these spacers required will depend on the lengths of the beams; usually 2 to 4 spacers are used in each beam.
Fig. 182. Spacer.