Lapping of reinforcing bars has long been considered an effective, economical splicing method. But today's more demanding concrete designs are forcing builders to consider alternatives. One such alternative is butt splicing using a mechanical connection, which consists of a sleeve to align bars and hold them in position. For tension connections and some compression connections, the sleeve transfers the tension or compression force directly from one bar to another. The connection of sleeve to bar is made by threading, swaging or filling the annular space between the bar and the sleeve with a molten metal.

Mechanical butt splices offer builders a number of benefits. They improve structural integrity, eliminate lap-splice calculations, reduce material costs and reduce rebar congestion. Also, they don't rely on concrete for load transfer. Because lap splices transfer load through the surrounding concrete, when the concrete is gone, the lap splice in effect has failed.