Valmiki Ramayana Bala Kanda Sarga 14 Shloka 26

तत्र there, यथान्यायम् as per shastras, प्रमाणत: with standard measurement, इष्टका: bricks, कारिता were made, शुल्बकर्मणि in the science of construction using a measuring rope, कुशलै: accomplished, ब्राह्मणै: brahmins, अग्नि: sacrificial fire place, चित: gathered and laid bricks were prepared as per standard measurment mentioned in shastras.

The sacrificial fireplace was constructed with bricks with standard measurement by brahmins who were experts in the art of measuring land with a string or single strand.