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, 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: