They used simple tools and bare hands only, and put the dirt into their pockets to avoid other members of the congregation noticing the tunnel.
Eitan Kalmovich, a congregation member, commented that, "Six men in their teens and twenties gathered money and hired a group of Mexican migrants to finish the work."
The workers lived in an abandoned building that included a ritual bath for men in the Chabad world headquarters for the duration of the project to help ensure secrecy. They lived there for three months and ensured the work was completed correctly, even installing support beams.
Another member of the congregation, who requested to stay anonymous, commented, "I was surprised at the amount of secrecy involved. I think it's impressive how they kept it under wraps. Yeshiva students are highly extremist and idealistic. Some of the students are here on residency permits and come from Tzfat, a holy city in Israel, thought to be the birthplace of Kabbalah (Jewish mysticism)."