Okay first off, you can only duplicate helmets, curaiss, boots, or gloves. ( no greaves or plaudrons, sorry!)
1) enchant an item to summon Helm, boots, curaiss, and gloves for constant effect.
Hint) I used a Ebony Tower Shield and called it Shield of Summonings.
2) equip the shield once you make it, back out of your inventory, then go back into you inventory once the summon is done and unequip the shield ( or what ever you enchanted.)
Hint) If you do it right the stuff you were wearing before the summon will be on you, but they will not be equipped.
3) Now Save and Load the Game.
4) when the game loads, you will still be wearing the same stuff, but you will have a duplicate in your inventory.
Hint) use this glitch to duplicate rare items such as the Daedric Face of God, the Cresent Blade, and many other rare and one-timer items.
5) have fun!! :gun: