Pin Block Holders are heavy duty aluminum extrusions that hold the Pin Blocks and Spacers. Two of the 8" Pin Block Holders are supplied as part of the 'Big Squeezy' Stretcher, and three larger sizes are also available. The larger two sizes can be used as a backstop, a 'deadman' without the need for any weight. Different width Pin Block Holders can be used on the same stretcher, with the wider end acting like an anchor, and the carpet moving more at the narrower end. Each Pin Block Holder includes two red End Caps and all screws. Each Pin Block Holder should have at least 1/3 to1/2 (15, 20 for No. 715-60, minimum) of its capacity (15, 30, 45 or 60) filled with Pin Blocks. A combination of Blank Pin Blocks or Spacers must be used to fill the remaining capacity. At least one Pin Block, or Blank Pin Block, must always be used next to each red End Cap. Pin Covers snap over the Pin Block Holders and will not fall off. Pin Blocks/Spacers are required and sold separately. Pin Covers are sold separately.