Antal Stopper Deck Blocks are a compact design with the level being fully concealed within the side plates and recessed fasteners. Not to be used under high loads, these blocks are intended for temporarily holding lines; with left and right versions available.

The sheaves are made from high strength resin, fitted with composite fibre bush and side ball bearings. No maintenance or lubrication is required. The side plates are made from a hard black anodized , high strength aluminium alloy; for wear and corrosion proofing and with all the edges smoothed off. The aluminium locking cam is fitted on an automatic opening spring: relaxing the sheet is sufficient to open the jammer.