Locking Component Templates
Before editing a component template, you should lock the component template. Locking prevents the component template from being edited by other users in parallel. The component template lock can be released manually. It is released automatically after the configured lock interval has expired. For details about how to configure the component template lock interval, see Defining Content Lock Period.
Basically, there are two ways to lock component templates: either directly from the component template list or tree, or via the Component Template detail view.