I cannot lock a dispenser ! Terrible. and the wiki clearly state. I have seen more problems with items i cannot lock, But i really need to have a locked dispenser !
You need to place the sign exactly above the dropper , needs to be: sign/air(i put air because most of the block space ,in which the sign is, is air Dropper
Thats all what i did, in wilderness and straigt above the dropper. "could not find lockavle item below the sign. unless you cannot lock a sign on wool with dispense runder it. Sign Dispenser Do locking all the time with chests. its on smp9
Ok, user error Above the sign where just different above the dispenser. Now i know what did go wrong all the time.