Reverse brick dominoes

[Father Kit Cool Gun Garth]

Never seen this before! 

 

 

 

[G W Wade]

Awesome   GW

[Pat Riot]

That is cool. I don’t think I have ever seen this before. 
 

In that second video there is someone saying to themselves “Now I now why it to so long for ABC Masonry to finish my wall.” 

[Marshal Mo Hare, SASS #45984]

The second video had a failure to fall at the end.

[Subdeacon Joe]

Several videos of this were posted here a year or two ago.  Here's one that shows some of the math.