Alwaysshoot your broadheads as mentioned here. It's just plain unethical to go out not knowing where your broadheads are hitting. Here is a good solution to your problem it's one I use, take a cardboard box layer it with old newspapers to the top and you have a very cheap target and at the least when your done, all you'll have to do is resharpen your heads, which you should do anyway before heading out to the woods