If you want to lock a variable to prevent it from being changed, use the Lock Symbols() function. (Lock Globals() is an alias.)
To release the lock and enable the global to be changed, use the Unlock Symbols() function. (Unlock Globals() is an alias.)
The primary use of these two commands is to prevent inadvertent changes to variables. For example, locking a variable prevents Clear Symbols() from clearing a variable that is being used by another script.