I remember when I tried to use a body modifier when it was first introduced and I don't know whether I did it wrong or it has been improved but I remember the frustration when it didn't work and I abandoned them as just another one of those items that may or may not work depending on which way the wind was blowing. Now I use them all the time to get simple things done in an effective way and I find them reliable and dependable.
OH NO! I just pulled out a photo!
It's not how I modelled it!!!!
That's okay, I'll just 'Restore' that Body Modifier, add some more ME to the WHOLE length of the wall, including the little vertical bits I had missed & union the whole ME together into one object. Then when adding the ME to the wall as a BM, select the replace option and it removes the course that would otherwise show (that we don't want).Now that I have a handle on Body Modifier's, I find them indespensible. They cleverly & efficiently solve many of the little modelling issues you come across in building virtual models. But wait ... there's more!!