  J. Tuma proved an interesting "congruence amalgamation" result. We are
generalizing and providing an alternate proof for it. We then provide
applications of this result: --A.P. Huhn proved that every distributive
algebraic lattice $D$ with at most $\aleph\_1$ compact elements can be
represented as the congruence lattice of a lattice $L$. We show that $L$ can be
constructed as a locally finite relatively complemented lattice with zero. --We
find a large class of lattices, the $\omega$-congruence-finite lattices, that
contains all locally finite countable lattices, in which every lattice has a
relatively complemented congruence-preserving extension.
