A children’s book from the 1970s or earlier. I am not sure of the title but it might be ‘Mr. Down’ or include the words ‘Mr. Down’. The setting is possibly medieval England. Townspeople are trying to build churches to pray in but every time they complete one, Mr. Down (a little troll-like guy or gremlin type character) comes in the night to stomp on the roof and destroy the church. They go through several designs all of which Mr. Down stomps on until they finally design an arch with a ‘keystone’ at the top. This is a classic Gothic style arch and no matter how much Mr. Down stomps, it will not collapse. I used to check this book out of a small Methodist church library in North Carolina every single summer of my childhood. It would mean the WORLD to me to find this book again.