Good idea.  I also need ability to do just that, question if I would have the guts to do that on a protector for barn area.(Can see it happening after the fact and getting manure between block and barn wall)  Already see weeds growing between wall and blocks that would require roundup clean up which have limited time to accomplish, without using them for pushers.  A block offers splash protection from the runoff on a roof that is not guttered.  Another problem of having barn as part of the pen.  Really think a row of blocks next to the barn might be a real possibility.  Have you ever seen a calf get on top of them?  Bawlers have a way of getting in trouble. They look like ideal scratching areas for cattle.  Indestructible.  It is endless what can be done with these blocks.  Add couple more to the list.  Thanks.