Masonry is one of the first 3 (or 4) skills you get in your skills panel. Its maximum level cap is 45, and to fully upgrade it would take 1035 skill points, and would waste 7,245 mana.
Whenever you upgrade this skill, you get -8% mana for buildings like walls, towers and amplifiers. Every three levels will give you -3% socketing time for gems. At max level of 45+15 you get -480% initial mana costs for buildings like walls, towers and amplifiers and +100% faster socketing time for gems.