A bell tolled 17 times inside St. Patrick’s Cathedral on Thursday. It echoed off the polished marble floors and the scrubbed limestone columns. It echoed off the hundreds of hard hats that were resting in laps, on pews and beside 16 roses on 16 empty seats at the altar.

The bell, forged by ironworkers from two unions, hung from a cross made of bent and mottled steel salvaged from ground zero. It tolled 17 times for the 16 construction workers who died in the past 12 months in New York City, and once more for those who had died since 2008, when the building trades began celebrating an annual memorial Mass here. There are 140 names now adorning the base of the cross, saints of a soaring skyline.

“There is understanding this is a sacred industry,” the Rev. Brian Jordan, chaplain for the Building and Construction Trades Council of Greater New York, said as he preached from the marble pulpit. “Our hands are sacred. Not just my hands as a priest, or as a piano player, as a violin player, or Stephen Curry, the basketball player. Everyone here who works in construction, you have sacred hands, and that’s why we appreciate you here today.”

Each April, on or around Workers’ Memorial Day, hundreds of construction workers file into St. Patrick’s, led up the limestone steps by a procession of bagpipers and the banners of their locals. Each April, their numbers swell.