Terminators (terminate symbols) in sequence diagrams snap onto the ends of activations and lifelines. Once snapped into place, they remain attached when the activation or lifeline moves or is copied. If the activation or lifeline symbol is deleted, the attached terminate symbol is deleted as well. Simply select a terminator from the style bar, drag it near the end of an activation or lifeline, and let it snap into place. (State symbols can also be snapped to lifelines in this manner.)