The present invention relates to a locking device primarily used for releasably joining two terminal end portions of jewelry items, although the locking device may also be used to releasably join two terminal end portions of non-jewelry items or the terminal end portions of two separate items. One embodiment of a locking device according to the present invention, for example, may comprise a first arrangement that includes at least one end portion that is at least partially open and an extension or a hole. The locking device may also comprise a second arrangement having a protrusion that is insertable into the first arrangement at the at least one end portion to place the first and second arrangements in a locked position. The locking device may also include a third arrangement that is connected to the second arrangement. In certain exemplary embodiments of the present invention, for example, when the third arrangement is acted upon, the third arrangement forces the protrusion to change in at least one of shape, size or orientation so that the protrusion is removable from the extension or the hole and cause the first and second arrangements to be in an unlocked position.