Source SDK: Mastering the Source/Edit Menu
The Edit Menu on the Control Bar houses a variety of useful tools that can assist you in creating your map.
Undo(CTRL+Z)
editThis button undos any action or edit you've made to anything in your level. The undo button has a limit.
Redo(CTRL+Y)
editThis button gives you the opportunity to redo an undo. The Redo button has a limit.
Toggle Undo/Redo
editThis button toggles ON and OFF your ability to use the Redo and Undo tools.
Find Entities(Ctrl+Shift+F)
editThis button opens a small search box that allows you to search any entity you have in your level, in case you have misplaced them. (add image of find entity search box)
Replace...(Ctrl+Shift+R)
editThis button opens a small search box that allows you to take any entity in your map and replace it with another. (add image of replace search box)
Cut(Ctrl+X)
editCuts a selected brush or entity out of the level and onto your clip board, for it to be pasted.
Copy(Ctrl+C)
editCopies a selected brush or entity out of the level and onto your clip board, for it to be pasted.
Paste(Ctrl+V)
editPastes whatever item you have in your clipboard onto the map. Because the button pastes the item as soon as you click it, making it difficult to aim where you paste it when using the drop down box, so it's smarter to use the hotkey.
Paste Special
editDelete(Del)
editDeletes any selected brush or entity within the map.
Clear Selection
editDe-selects any brush or entity you have selected in the map.
Select All
editSimultaneously selects all brushes and entities in the entire map.
Properties
editShows the current properties of a selected entity.