Slipforms consist of inner and outer sheathing (form), 3.5 to 6 ft (1.07 to 1.83 m) high, using 1 in. (25.4 mm) thick lumber. Forms may be fabricated from wood or steel. The sheathing is not fixed to the floor; instead it is suspended either from several lifting devices supported on metal rods, or from other members resting on the foundation or on hardened concrete by means of wooden or metal yokes (frames). Once the form has been filled with fresh concrete and hardening has started, the form is gradually raised by the lifting devices on which it is suspended.
Yokes are normally made of steel or wood. The function of yokes is to transfer the entire loads of decks and supporting scaffolding into the jacks and the jack rods.