The Locked property determines whether a
BasePart|part (or a
Model|model it is contained within) may be selected in Roblox Studio by clicking on it. This property is most often enabled on parts within environment models that aren’t being edited at the moment. Roblox Studio has a Lock/Unlock All tool that can toggle the Locked state of every part descendant in a model at once.
This code sample uses the concept of recursion to unlock all parts that are a descendant of a model.