Pier columns

[Tucker61]

The top of the pier columns at my sons house were loose, so we removed them today ready to clean up and return.

Underneath the top slab appears to be a tile that is roughly 6 inches square.

What is the purpose of this tile ?
Are these tiles needed? And if so what are they called ?

Thanks in advance.

 

[23vc]

Is this a garden wall? Creasing tiles but actually quarry (in your case) or roof tiles

 

[Tucker61]

Thanks, yes it is a garden wall