We present the design and the implementation of clp(B): a boolean constraint solver inside the Constraint Logic Programming paradigm. This solver is based on local propagation methods and follows the "glass-box" approach of compiling high-level constraints into primitive low-level ones. We detail its integration into the WAM showing that the necessary extension is truly minimal since only four new instructions are added. The resulting solver is around an order of magnitude faster than other existing boolean solvers.