When working with external references in SolidWorks, it is extremely important that users understand the differences between Lock All and Break All. These functions, added in SolidWorks 2000, are for managing the associativity of features that are related to other part files or built in-context in an assembly. The functions are accessed by opening a part file that has external references. Place your cursor over the top-most icon of the FeatureManager, right-mouse click, and select "List External Refs". At the bottom of the External References dialog are three buttons: Break All, Lock All, and Unlock All.
The Lock All and Unlock All buttons are very useful. Imagine that you are building two parts that fit closely together, such as the two leaves of a door hinge. Top-Down design techniques will allow one leaf to automatically update when you make changes to the other side. However, if you wanted to animate the hinge, and do motion of collision studies, this could cause difficulty -- each time you dragged one hinge leaf into a new position, it could update the other hinge's shape. So there are times when you want to temporarily prevent the top-down update process. Lock All does that. External references that are locked do not update with changes to the referenced file. Unlock All, of course, returns the model to normal updating.
Break All functions exactly the same as Lock All with the important difference that there is no Unbreak All button! This button is offered as the lazy man’s way of removing external file references. It is tempting to use this, instead of manually editing each sketch and top-down feature, to replace the external relationships with internal ones. However, at sites where large-scale product design is done collaboratively over the network, and where parts that have been subjected to the Break All command are used, CAPINC engineers have seen this feature can lead to corruption issues which usually result in the inability to open the top-level assembly file at all. It is CAPINC's recommendation that users do not use the Break All button. Not ever. Never.
