The Mechanic is part of the supply production of your colony. The Mechanic will craft redstone items, rails, minecarts, clocks, compasses, sea lanterns, torches, lanterns, jack-o-lanterns, storage blocks (like blocks of iron, coal, quartz, etc), blue ice, packed ice, enchantment tables, ender chests, tripwire hooks, sticky pistons, gates, multi-pistons, anything made with blaze rods, and many other items that no other crafter can make. They will only make these items when they have been taught the recipes, receive a request for an item, and have the needed materials.
Note: The Mechanic can only learn a set number of recipes based on their hut level. So: