If all of your bags are full and you drag and drop a 2h weapon on top of your existing single handed items it will stack with them. This works with swords and shields as well as totems and such. You must use the bank to hold it for the drag and drop, of course.
alternate method...
First find your offhand item while wearing a 2-hand. Next go to the bank and put the offhand item in the bank. After that fill up your inventory. When your inventory is full, drag/drop the offhand from the bank to the equip slot. It will now equip, and since your inventory is full, it can't unequip itself. Rinse and repeat with the mainhand... makes for some INSANE spellpower on my mage. Gonna miss this one when they fix it.
stats is specifically what this is for but if you do it right you can attack with the mainhand solely or with the twohand depending on which starts the trick and which is dropped over top. if you have epics this is pure win. You can make new toons and lock the swimming address to do all the puzzles transferring the loot to your main. at level 6 stillmore, shimmersand and iron pine peaks yield level 35 and quite often epics. Just one bit of advice. Do not speedhack or teleport in acquiring the puzzle locations. Take your time. If you do either of those and garner the attention of the GMs they can parse your data log and tell you were doing it. Once caught you will be on a watch list and are pretty much barred from ever doing that sort of thing again. I know this cause my second account is now on a 72 hour ban for it. Stay safe.
Oh, the puzzles yield greens to epics of flavors 15, 20, 25, 30 and 35 when you are level 6 but i listed those three because the epic 35's scale well against most greens and blues almost to 50. Doing lantern hook right now and nothing that drops is worth my time in comparison. Just a tip if you have the capabilities. If not, just using greens stacked this way is more than typically OP for whichever class.
you can wear a 1-hander, 2-hander, and an offhand item all at once!!! Four hands!!!!

Once complete you can empty your bags without losing the glitch.
just need someone else to confirm it so we can relocate this post out of the public eye, please.