An old canoe, tipped over ;) That's what they have at this hunter pace I'm going to this weekend -- fun times!! Also other ones we've used...
* lattice leaned up against some orange cones
* tarp laid over the lattice
* tires are always good, and you can dig a trench and half bury them so that they stay put
* barrels or oil drums
* bales of hay
*pumpkins (it's getting to be that time of year!) all in a row or even stacked up on each other like a wall :)
* logs or branches
The possibilities are endless!!