Depends on the material used. But if you are looking for quick sheathing/unsheathing of your sticks, it probably won't happen. Obviously, you want the sheaths to be tight on the weapons so that they don't rattle around, but that means having an opening in the material only slightly larger than the width of the weapon (in this case, a narrow stick). So unless you want to spend hours practicing blindly sheathing your sticks on your back, training your muscles to know exactly where that opening is, quick storage is near impossible.
This is one of the more prominent points where comic book/Hollywood physics strongly comes into play. Back sheaths are just impractical. If a character has a long, slender, rigid object (two 26ish inch sticks in this case) sheathed on their back, he/she essentially has a spinal brace. The spine moves and bends, fabric moves and bends with it, but swords and sticks won't. What this means for us cosplayers is that you either have to be ready to have a straight back for much of the day, or you risk ruining your sheaths or your costume by putting extra stress on the material housing them (depending on the material).
Now that the obnoxious, discouraging, boring logic stuff is out of the way...
Magnets- The easiest way I've seen this done was to use high powered magnets, with one part attached to your garment on the back, and the other attached to the stick. Reach back with the stick, hover around the area where the magnet should be and eventually *click*. Pros: Pretty quick storage, still allows you to bend your spine mostly. Cons: The sticks don't always hold a static position, the magnets can fall off the costume or damage the fabric depending on the fabric used.
Pocket sheaths- Picture the breast pocket on a mens dress shirt, and you will get an idea of how these are supposed to look. In this case, the "pockets" are longer and less wide. Pros: Keeps sticks secure by housing most of the stick body, holds position. Cons: harder to sheath without looking, can be uncomfortable.
Sleeve sheaths- Essentially a tube of fabric/material, attached (via sewing or otherwise) to the garment to hold the weapon. Pros: Keeps sticks secure by housing most of the stick body, holds position, lease conspicuous. Cons: Very difficult to sheath without looking, can be uncomfortable.
The one other way I have seen it done is with Velcro. The cosplayer lined part of his sticks in Veclro and then sewed two wide strips on to his back so that he could just throw the sticks back there and they would stay. It was a clever idea for achieving the effect, but not necessarily the most attractive.
Hope that all helps!
