Abstract: This invention relates to a closure cap, a container and to a closure cap and corresponding container in combination. As shown in FIG. 1 of the drawings, screw threads 14, 22 of a cap 2 and container 4 respectively each have sufficient alternate ridges 16, 27 and indentations 18, 28 over at least part of their length so that when the cap 2 and container 4 are in a closed position, at least one ridge on one screw thread can engage an indentation on the other screw thread. In another embodiment of the invention as shown in FIGS. 8 and 9, the screw thread of the cap is formed by a series of rounded projections 68 that are located adjacent to one another and overlap slightly with one another. The rounded projections 68 have a series of alternating rounded ridges and adjacent indentations.