Mini Toolbox Double Stack (Harbor Freight)

Toolbox Stacking Frame: Secure, Reversible, and Seamless

This frame securely holds a second toolbox on top of another toolbox. There are no permanent attachments, and the setup is completely reversible — just lift off the top toolbox when needed. Because there is no gap between the toolboxes, the finished look is like a solid bank of four drawers.

The basic C-shaped pieces slot together with dovetails. The included print profile uses a few supports that should remove with minimal effort. The dovetails are intentionally tight, so the frame should be a friction fit with no glue required, though it may take a few strokes with a razor to fine-tune the fit.

Included shims can lock the frame in place for zero movement between the two boxes. Since toolbox sizing can vary slightly, the shims may need adjustment to match your specific toolboxes.

A lid brace is also included. It fits between the bottom lid and the back of the top toolbox, where it does two things: it pushes the top box forward by about 1mm to remove slop, and it protects the bottom lid from scratches when the top lid is opened and closed. The brace stays in place with a pair of 6x3mm magnets, and it slides down until the desired gap is set.

Required hardware:

• 4x 6x3mm magnets (6x2.75mm actual)

Note that the exact dimensions of these boxes has changed at some point in the past.  To tell the difference between the new ones and the older ones, look for the plastic bumpers on the lid.  The new one will have small black ones while the older one will have larger clear ones that extend beyond the edge of the lid.  This model is made to fit the newer boxes.  It will fit exactly into the 4 boxes that I purchased around 8/2025 as well as the boxes that I picked up around 4/2026.

More details and some date codes can be found here: