The 2 pillars are from Solomon's Temple, designed by David
Jachin and Boaz stood at the entrance to the temple’s vestibule or portico. Their dimensions indicate the extent of the work involved in creating them. Including the decorative tops of the pillars, Jachin and Boaz stood approximately thirty-five feet tall, with a circumference of eighteen feet (1 Kings 7:15–20). The brass used to make the twin pillars had been taken by King David from the king of Zobah as part of the spoils of war (1 Chronicles 18:8–9).
The pillar on the south of the entrance which was called Jachin, and one on the north named Boaz. Both 2 Chronicles and 1 Kings say that “he” set up the pillars and “he” named them Jachin and Boaz. Commentators are divided as to whether “he” refers to Hiram or Solomon. Whoever named them, their names are significant. Jachin (pronounced yaw-keen) means “he will establish,” and Boaz signifies “in him is strength.” Taken together, the names were a reminder that God would establish the temple and the worship of His name in strength.
https://www.gotquestions.org/Jachin-and-Boaz.html