Building a drawer box to fit a cabinet opening is a game of precise measurements. Here’s the manual process:

1. Measure the Cabinet Opening: Carefully measure the width of the cabinet opening where the drawer will be installed. Take measurements at the top, middle, and bottom, and use the smallest one.
2. Check Slide Specifications: Look at the manufacturer's specifications for your chosen drawer slides. They will list a required 'side clearance'. This is the amount of space the slide hardware itself occupies.
3. Calculate Total Clearance: For side-mount slides, you have two slides, so you must double the listed side clearance to get the total clearance needed. (e.g., 1/2" total for two slides that each require 1/4").
4. Determine Drawer Box Width: Subtract the total clearance from the cabinet opening width. This is the exact outer width your drawer box needs to be.
5. Select Slide Length: Drawer slides come in standard lengths (e.g., 18", 20", 22"). Choose a slide length that is equal to or slightly less than the interior depth of your cabinet.

• Drawer Slide: A mechanism that allows a drawer to move in and out of a cabinet smoothly.
• Side-Mount Slide: The most common type, where one member mounts to the cabinet side and the other to the drawer side. Typically requires 1/2" of total clearance.
• Undermount Slide: Mounts underneath the drawer box, making the hardware invisible. They offer a cleaner look but have specific drawer construction requirements.
• Center-Mount Slide: A single slide that mounts under the center of the drawer. Typically used for smaller, lighter drawers.
• Clearance: The amount of space that must be left between the drawer box and the cabinet opening to accommodate the slide hardware.
• Full-Extension vs. 3/4 Extension: Full-extension slides allow the drawer to pull completely out of the cabinet, while 3/4 extension slides leave the back quarter of the drawer inside.

"The cabinet itself is your reference. Before you even build the drawer box, make sure your cabinet is square. Use a good square to check the opening. If the opening is not square, your drawer will never run smoothly, no matter how perfectly you size it. I always build the cabinet carcase first, measure the final, assembled opening, and only then do I build the drawer box to fit that specific opening. Don't build the box based on the plans; build it based on the reality of your cabinet." - Professional Cabinetmaker

Standard Kitchen Drawer: Your cabinet opening is 18" wide and you are using standard side-mount slides that require 1/2" total clearance.
Required Drawer Width = `18" - 0.5" = 17.5"`. You must build your drawer box to be exactly 17.5 inches wide.

High-End Dresser with Undermount Slides: Your cabinet opening is 30" wide. Undermount slides typically require a total clearance of 3/8" (3/16" per side).
Required Drawer Width = `30" - 0.375" = 29.625"`. The drawer box needs to be exactly 29 5/8" wide for the slides to function correctly.

• Forgetting to Double the Clearance: A common error is subtracting the clearance for only one slide, resulting in a drawer that is too wide.
• Building the Drawer Before the Cabinet: Building the drawer based on a drawing's dimensions, rather than the actual cabinet's dimensions, can lead to a poor fit.
• Not Accounting for a Face Frame: If your cabinet has a face frame, you may need to install blocking inside the cabinet to provide a mounting surface for the slides that is flush with the opening.
• Ignoring Slide-Specific Requirements: Undermount slides often have specific requirements for the drawer box itself, such as a notch at the back or a specific bottom panel recess. Always read the instructions.

• Kitchen & Bathroom Cabinets: Ensuring drawers for pots, pans, and utensils fit and slide correctly.
• Dressers and Nightstands: Building furniture with smooth, reliable drawers.
• Workshop Storage: Creating custom drawer units for tools and supplies.
• Office Furniture: Building file cabinets and desk drawers that can handle heavy loads.