The Builder's costume is worn by builders. It is acquired during the Tower of Life quest, and consists of a Hard hat, Builder's shirt, Builder's trousers and Builder's boots. When any piece of the costume is worn, the Beckon emote will be enhanced, should the player use it.
While needed during the quest, it is not required when the quest is completed.
The builder's costume can be stored in an armour case in the costume room of a player-owned house. After the quest, you can get the costume pieces by searching the crates on the ground floor of the Tower of Life or by doing the tasks necessary for each piece again (answering questions for the helmet, searching plants for the trousers, giving 'The Guns' a beer, and pickpocketing 'No fingers' for the boots).