You can lock files in order to prevent other users from delivering changes to the files while you are working on them. This is especially useful for files that can’t be easily merged, such as bitmaps.
To lock files, select the files to lock in the Solution Explorer and select Lock. To unlock files, select the locked files from the Solution Explorer and select Unlock. Locked files are also unlocked by default when users deliver changes to the locked files.
Locked files appear with a red check mark. If another user has locked the file, the file appears with a red check mark and exclamation point.