22
Stacker 3
Remove
Hold the handle, lift it up, and then pull towards you to take out. 
Attach
Hold the handle, line up the indentations, and attach. 
 When you insert Stacker 3, first check that there are no discs in Stacker 4, and then 
attach it. 
 When you use Stacker 3, set the lock to [LOCK], and do not pull out Stacker 4.