Abstract: Edge-dam blocks assembled with their upstream faces in keyed mating interengagement with downstream faces of adjacent blocks form an endless edge dam revolvable in a preselected path for defining a boundary of a moving-mold casting region. The edge dam keeps molten metal in the casting region. Upstream and downstream faces of adjacent blocks have mutually complementary shapes for minimizing intrusion of molten metal between abutting blocks. Keying engagement between abutting blocks prevents relative translational slippage of blocks toward or away from molten metal. An abuttable face on each block has at least one protrusion such as an integral elongated key extending perpendicularly to a casting belt associated with the casting region, or the protrusion includes two round pins having projecting tapered ends. Another abuttable face has a recess such as a keyway for snugly receiving a key on an adjacent block or has two tapered recesses for snugly receiving two tapered projections of an adjacent block.