As in most other finely-fitted megalithic structures, those rough protrusions were likely used for transporting and bracing the fitted stones in place until the meeting of the stones at the top of the corbel were capable of supporting the lateral thrust forces.
Once the walls "closed" at the top of the corbeled arch, the network of supporting wooden braces or props were removed.
In more sophisticated constructions (like the "Atreus" or "Agamemnon" Kurgan), those rough "construction handles" were chiseled and polished away.
In truth, we are fortunate to have these clues to early construction techniques left intact -- in this particular case -- for us to study and analyze.
Just imagine how difficult it would be to transport and brace those stones -- if the rough "handles" were already cut and polished away! (That's how theories about ancient "stone levitation", etc. ad nauseam wacko stuff gets started...) :-(
Most of the "Mysterious Megalithic Stonework" garbage is due to "modern" folks who simply refuse to accept the practical ingenuity -- and patient craftsmanship required to finish the job -- displayed by (with a sneer) "primitive" civilizations...
Quite frankly, I'm much more in awe at out ancestors' cleverness!
TXnMA </SOAPBOXMODE>
