Abstract: An electrical terminal block whose base has four or more lugs projecting downwardly from a generally flat under-surface for locking the block against a fixed support having edges which are co-planar, in a plane parallel to the block's undersurface; at least two of the lugs being formed with opposed channels, each open at one side for receiving and laterally abutting against one of two corresponding oppositely-extending edges of the fixed support so as to lock the block against the support, at least two others of the lugs being stops for laterally abutting corresponding edges of the fixed support; whereby the block may be fixed to the support by resting its undersurface against the block and twisting it in the plane of the undersurface until all the lugs are in abutment against the corresponding edges.