From Xojo Documentation
Determines whether the top edge of the control should stay at a set distance from the top edge of the parent control, if there is one, or the owning window.
Beginning with version 2009r5, LockTop and LockLeft default to True when you add a control to a window. Existing controls will be altered only if LockRight and/or LockBottom are not set. LockTop has no effect unless LockBottom is True.
This control can be set in the control's Inspector. The following example sets it in code.