Professional needed?

[saveasteading]

Yes, no, as long as possible, yes.

It is a "tell-tale"

 

I think glued is preferred as it doesn't twist.

 

[SteamyTea]

2 hours ago, Reggie1 said:

Should I use one of these

How good are you at keeping records?

 

Could easily make your own 

Edited 2 hours ago by SteamyTea

[saveasteading]

44 minutes ago, SteamyTea said:

Could easily make your own

I wouldn't. It is a well made , fit for purpose, and precise thing, and I don't think expensive.

 

The only issue would be if the crack has completed its shrinking and starts to close again when the rains come. I think it would just shatter then, but still a point proven.

Maybe glue one side only and take measurements and photos to account for this happier possibility.