U/c grounf locks, history and specs research query
 

Possibly one of the more obscure queries posted on here, but, hopefully, some relevant facts may emerge.

In essence, I am trying to help a friend engaged in a research project regarding the introduction, development, material specs, design(s), loadings and overall history / origins of the humble u/c ground lock.

Not the most enticing of subjects I know, but, any reference material, guides, or indeed design knowledge would be appreciated please.

Also being posted on the Engineers forum.

Many thanks.

K n C