When using 4D Server, object locking occurs when two or more users attempt to modify the same form simultaneously. If a user is modifying a form in the Design environment, the form is locked. Other users cannot modify the same form until the first user frees the form by closing it. Once the first user closes the Form editor, another user can either quit and load the form or click on the red lock button in the tool bar to gain read and write access.
The lock button also appears in the Method editor when trying to modify a locked method.