This paper is a continuation of [7], where a duality theorem for the category HLC of locally compact Hausdorff spaces and continuous maps is proved. In the present paper, we characterize the injective and surjective morphisms of the category HLC, as well as of its cofull subcategories determined by the open, by the skeletal or by the perfect maps, by means of some corresponding properties of their dual morphisms. This is in analogy with some well-known results of M. H. Stone [17] and generalizes some similar results of de Vries [4]. Such characterizations are also obtained for the homeomorphic embeddings, dense embeddings, LCA-embeddings etc.; in particular a theorem of Fedorchuk [10, Theorem 6] is generalized. Again in analogy with some well-known results of M. H. Stone [17], the dual objects of the open, regular open, clopen, compact open, regular closed etc.subsets of a locally compact Hausdorff space X are directly described by means of the dual object of X; some of these results are new even in the compact case. An explicit description of the products of local contact algebras (= LC-algebras) in the category DHLC dual to the category HLC is given and a completion theory for LC-algebras is developed.