ToolStripMerging is driven through two different mechanisms: Automatic (MDI) and manual. This section covers top level concepts in both of the mechanisms. The rules of how the items merge do not change for these two methods, just the triggering mechanism. MergeActions are evaluated on a per item live basis – the last one in affects the next. Another key difference between MainMenu merging and MenuStrip merging is the fact that items are physically moved from one ToolStrip to another rather than cloned as is the case with MainMenu.

Manual merging is accomplished by calling ToolStripManager.Merge() and RevertMerge().