The icon for the Masonry skill.
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.
Skill Attributes[]
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.