LCS supports three methods of working with differences:
Right-clicking in the document area will bring out a popup menu with a list of all available operations. This is a sure-fire method that is suitable for all users but requires a few extra clicks and mouse movements.
Alternately, it is possible to simply drag a diff block to the other side and drop it to copy it.
This is a fast method that requires only one click per operation. If the auto-popup option is enabled (see the Edit » Options... menu item) then moving the mouse over the rightmost area of a difference block will automatically popup a mini toolbar with buttons that allow you to copy or delete the block.
The fastest and most powerful method is targeted to the more advanced user and uses keyboard and mouse at the same time. The concept is simple: while the mouse pointer is over a difference block you may press a key to execute an action on that block, as shown in the following table:
| Key | Action |
| A | Advance to next page (this is actually a duplicate of the PageDown key) |
| C | Copy block |
| D | Delete block |
| Z | Undo copy or delete on a modified block |
| 1 | Merge from left document: block is copied if it belongs to left document, deleted if it belongs to right document |
| 2 | Merge from right document: block is deleted if it belongs to left document, copied if it belongs to right document |
All the above keys can be used with one hand only.