Abstract: Tool trays (46, 48, 50, 52) are fittable into inner compartments (18, 20) in carrying case parts (12, 14). A plurality of lugs (L) on the side walls of inner compartments (18, 20) in the carrying case parts (12, 14) cooperate with a light number of sockets (S) in wall portions of the tool trays (46, 48, 50, 52). The tool trays are snap-fitted downwardly into the inner compartments (18, 20). As the tool trays (46, 48, 50, 52) move downwardly, the lugs (L) move into the sockets (S). When the trays (46, 48, 50, 52) are within the compartments (18, 20) the upper end portions (44) of the lugs (L) will be above end wall portions (66) of the sockets (S). They will be positioned to block unwanted movement of the holders (46, 48, 50, 52) out from the inner compartments (18, 20). However, the trays (46, 48, 50, 52) can be easily pulled out from the compartments (18, 20). The lugs (L) and sockets (S) act as detents for removably securing the trays (46, 48, 50, 52) within the inner compartments (18, 20).