This spell was cast on a non-metallic item before the caster cast a second spell of their choosing into the item. The caster's second spell could be any spell from their repertoire, or any other spellcaster could cast the second spell if they touched the item during casting. The target item could not already have an enchantment upon it.
Whoever wore the item holding the disrobement was aware when the spell was going to go off and could even prevent it if they desired even if they lacked spellcasting abilities. They could also control the spell with regards to target selection and any other variables the spell had. All of these controls were mental acts by the individual so they could be accomplished even when gagged. The individual was also always immune to the effects of the spell.