The Metalworking Bench is a block that allows the player to perform Sword Customization. It was added in Minecraft 1.18. It is crafted by combining a crafting table and 4 cobblestone.
The GUI has four buttons above for blade types, with four buttons below for hilt types. A slot on the top right to place blade material, a slot below that for hilt material, and a slot below that for gem material which can only be used if the player has equipped the bejeweled hilt type.
The bottom left slot is where the player puts their uncustomized sword, and the right output slot allows the player to claim their sword once it's customized to their liking.
If the player breaks a customized sword and wants to reforge it, they can put the swords' material into the sword slot to reclaim a very badly damaged version of their sword, which will need to be repaired.