Will the fastener be placed in (a) the mortar joint, (b) the solid section of the block or (c) the hollow section of the concrete block? Some applications may allow each fastener to be placed in the same part of the block while other installations require that each anchor is placed in different sections of the block.
Sleeve anchors Best for medium-duty applications in concrete block. Length is measured from the washer to the end of the anchor. Sleeves pinch the side of the pilot hole and get tighter as the screw is driven into place. Toggle bolts Best for light to medium loads in hollow block.