We have a couple of hawk blocks at our archery club Hawkeye Bowmen. At our Primitive shoot in the spring we have a hawk and knife throwing competition where you have to cut a playing card or a string.
The best challenge I ever saw was, a round block on a ramp held by a string, you had to cut the string with your hawk and pull your knife from your belt and stick it in the block as it rolled down the ramp.
Kevin