A drawing by Cyril Fox suggesting how an upside down cruck could be formed from an oak tree.

Cruck frames made from oak trees were an essential part of many medieval homes and held the weight of the roof.

Cyril Fox and Lord Raglan claimed that the timber needed to be used upside down to the way it grew when it was a tree.

Iorwerth Peate disagreed, and claimed that crucks must be used in the way they grew. Further research has shown that Peate was correct.