करणी

स्त्री० [सं० करण+ङीष्] १. करण नामक संकर जाति की स्त्री। २. गणित में, वह संख्या जिसका पूरा-पूरा वर्गमूल न निकल सके

That He may know that they have indeed conveyed the messages of their Lord. He surroundeth all their doings, and He keepeth count of all things.

The mason is using the trowel in the construction.