Go to the guy who gives the tonk daily (Finlay Coolshot) and press the "Ready to play!" option. Then push the tonk against the outer fence until you get out (very easy to do).
You can no go anywhere you want with the tonk, and when the time runs out, your character will be teleported to where the tonk died.
Also, you can go to the arena gate as the tonk and right click it, and your character will be teleported inside.
The only use i can see in this is that you can enter the arena sneakily and kill people who wouldn't have entered the arena if they saw you there.
Maybe there are other things you can do with this, i'm currently trying to figure out if this could somehow be used to glitch under the arena since the tigers were nerfed.