A method of latching a tube (11A, 11B, 11C, 12A, 12B, 12C) against movement of the tube relative to an external element (10, 11A, 11B, 12A, 12B), where the tube has two substantially parallel side walls (16, 17) with inside surfaces of the side walls (16, 17) spaced by a hollow interior of the tube, at least one of the side walls (16, 17) of the tube having a hole (21, 22) therein; the method of latching comprising: inserting a housing into the tube longitudinally of the tube from an open end of the tube with ends (31, 32) of the housing spaced by a distance substantially equal to the spacing between the side walls (16, 17), such that the housing can slide into the interior of the tube between the side walls (16, 17) with the ends (31, 32) of the housing substantially butting inside surfaces of the side walls (16, 17); moving a slide member in the housing longitudinally of the housing and therefore transversely of the tube by depressing a button on the slide member; the slide member being movable from an extended position of the button projecting outwardly from one end of the housing through the hole (21, 22) for engagement with the external element to prevent movement of the tube relative to the external element to a depressed position of the button to release engagement with the external element; resisting the sliding movement of the slide member by at least one spring as the button is moved to the depressed position; providing at least one stop member which operates to engage the slide member to prevent depression of the button to a position within the inner surface of the side wall (16, 17) so as to prevent movement of the housing within the tube, with the stop member being removed from operation, moving the housing into place within the tube from the open end of the tube to said hole (21, 22), with the housing in place within the tube at the hole (21, 22), positioning the stop member so as to a) prevent depression of the button to a position within the inner surface of the side wall (16, 17) so as to prevent movement of the housing from said place; and b) allow depression of the button to said depressed position of the button in which the button is released from engagement with the external element to allow movement of the tube relative to the external element. inserting a housing into the tube longitudinally of the tube from an open end of the tube with ends (31, 32) of the housing spaced by a distance substantially equal to the spacing between the side walls (16, 17), such that the housing can slide into the interior of the tube between the side walls (16, 17) with the ends (31, 32) of the housing substantially butting inside surfaces of the side walls (16, 17); moving a slide member in the housing longitudinally of the housing and therefore transversely of the tube by depressing a button on the slide member; the slide member being movable from an extended position of the button projecting outwardly from one end of the housing through the hole (21, 22) for engagement with the external element to prevent movement of the tube relative to the external element to a depressed position of the button to release engagement with the external element; resisting the sliding movement of the slide member by at least one spring as the button is moved to the depressed position; providing at least one stop member which operates to engage the slide member to prevent depression of the button to a position within the inner surface of the side wall (16, 17) so as to prevent movement of the housing within the tube, with the stop member being removed from operation, moving the housing into place within the tube from the open end of the tube to said hole (21, 22), with the housing in place within the tube at the hole (21, 22), positioning the stop member so as to a) prevent depression of the button to a position within the inner surface of the side wall (16, 17) so as to prevent movement of the housing from said place; and b) allow depression of the button to said depressed position of the button in which the button is released from engagement with the external element to allow movement of the tube relative to the external element. a) prevent depression of the button to a position within the inner surface of the side wall (16, 17) so as to prevent movement of the housing from said place; and b) allow depression of the button to said depressed position of the button in which the button is released from engagement with the external element to allow movement of the tube relative to the external element.