In sailboating and shipbuilding, Mast Stepping is the process of raising the boat's mast. It also refers to a ceremonial occasion which occurs when the mast is stepped, towards the end of a ship's construction. The ceremony involves placing or welding one or more coins into the mast step of a ship, and is seen as an important ceremonial occasion in a ship's construction which is thought to bring good luck. Although the coins were originally placed under the main-mast of a ship, they are now generally welded under the radar mast.
Mast Stepping Wikipedia
The ceremonial practice is believed to originate from ancient Rome. One theory is that, due to the dangers of early sea travel, the coins were placed under the mast so the crew would be able to cross to the afterlife if the ship were sunk. The Romans believed it was necessary for a person to take coins with them to pay Charon, in order to cross the river Styx to the afterlife and as a result of this, coins were placed in the mouths of the dead before they were buried. Another theory for this practice is that the insertion of coins in buildings and ships may have functioned as a form of sacrifice thanking the gods for a successful construction, or a request for divine protection in the future.