Effortless 3-Way Adjustability: Adjusting your door has never been easier! Our innovative 3-way adjustment system lets you fine-tune the position in/out, left/right, and up/down with the included hex key. No need for re-drilling or re-measuringjust a quick adjustment to perfect your door alignment and save you installation time.Perfect for Hidden Doors and Custom Projects: These hinges are the perfect choice for a variety of custom projects, from hidden bookcase doors and secret passageways to bifold doors and DIY secret door designs. Their smooth, invisible operation makes them ideal for creating sleek, seamless entrances without visible hardware.Important Installation Notes: For proper installation, ensure the area where the hinge will be placed is not hollow. A 1-inch wide by 7/8-inch deep slot needs to be carved into both the frame and the door to accommodate the hinge. Please check the thickness of your door beforehand.Completely Concealed Design: Once installed, these hinges remain entirely hidden from view. With no protruding pins or parts, you can place the door anywhere without compromising on aestheticsideal for creating seamless hidden doors or hidden bookcase entrances.Heavy-Duty, Quiet Operation: Crafted from durable zinc alloy with a sleek black finish, these hidden door hinges are built to last. Capable of supporting doors up to 88 lbs, they offer a smooth 180-degree swing with quiet, creak-free operation, ensuring both style and functionality.