When an insert makes sense
If a toolbox already works but its contents are a jumble, you can often fix the problem without touching the box. A removable insert, made of one or two lift-out trays and some dividers, sorts the small items that otherwise sink to the bottom: screws, bits, drill bits, nuts, pencils, small pliers and the like. The box stays as it is, and the insert can be modified or replaced when your tools change.
This is a different project from a box that has its compartments built into the walls, which is a better choice if you are starting from scratch. An insert is the right answer when the box is already in use, when it is a store-bought box you do not want to modify, or when you want the freedom to rearrange.
Measure the box
Accuracy matters here because the insert has to slip in and out without sticking. Measure the interior length, width and depth in several places, since inside dimensions are rarely identical along their length. Look for features that interfere with the insert, such as hinges, latch hardware, ribs or a tapered wall. Use the smallest measurements you find as your limits.
Write down the measurements, then decide how much of the depth the insert should use. A tray that fills the top inch or two of the box leaves space below it for larger items. As a hypothetical example, a box with a 16-inch by 6-1/2-inch interior could take a tray 15-7/8 inches long and 6-3/8 inches wide, which leaves one-eighth of an inch of clearance in each direction (16 minus 15-7/8 is 1/8, and 6-1/2 minus 6-3/8 is 1/8). A little play is useful, because wood swells slightly with humidity and a snug fit can bind. Use your own measurements instead of the example.
Choose materials
Thin materials are best, since the point is to gain organization and not to lose space. Solid wood strips, thin plywood and hardboard are all workable, and thin plywood tends to be a common choice since it is flat and stable. Use stock that is thick enough to be stiff, but thin enough to leave room inside the compartments. Keep in mind that thin plywood is not always as thin as its label says, so measure the actual sheet before planning slots.
Building a lift-out tray
A tray is a shallow, open-topped box with a bottom. It can rest on cleats attached to the box’s end walls or, if the box has a flange or lip, on the top edge of the box itself.
- Cut the sides and ends to the tray size you calculated. Sides that are 1 to 2 inches tall suit most small parts, though your selection of items may call for something shallower or deeper.
- Assemble the frame with glue and small brads or screws. If using screws, drill pilot holes to prevent splitting thin stock, and take care not to break through the outside face.
- Add the bottom from thin plywood or hardboard, glued and fastened to the underside of the frame. Check that the tray is square by measuring the diagonals.
- Add support cleats inside the toolbox if the tray needs something to rest on. Fasten them with glue or screws, depending on the box material, and follow the box maker’s guidance if you are not sure whether the walls can be drilled.
- Add a finger notch or a loop at one end so the tray lifts easily.
Test the tray in the box before you subdivide it. It should drop in without catching, come out easily, and sit level.
Making dividers
A fixed divider is a strip of thin material glued across the tray. It is simple and strong, but you cannot move it. An interlocking grid lets you rearrange compartments.
To make a grid, cut two sets of strips to the length and width of the tray and to a height a little less than the tray sides. In each strip, cut slots halfway through the height, and make them spaced to match where the strips will cross. Fit the pieces together, and each strip locks the others in place. This is a version of the half lap joints used in woodworking, and it needs no glue at all. The slot width should match the strip thickness, so test it on a scrap piece. Cut the slot a hair loose, since a tight slot will split thin strips or won’t go together at all.
If you cut the slots with a saw, make them just inside the line, and trim to fit using a file or a piece of folded sandpaper. A fine sandpaper grit smooths the edges so nothing snags.
Customizing for what you carry
Different items need different compartment sizes. Small hardware benefits from many small cells. Drill bits and driver bits fit well in a block with drilled holes, or in a shallow tray with a strip of foam. Items such as screwdrivers and pliers want long, narrow slots. A magnetic strip fixed to the inside edge of a tray can keep small steel items from rolling. Putting the right tool in the right cell is the point. Grouping pliers types together and sorting fastener types by size makes each cell easy to find.
Sockets are best on rails or in a dedicated socket organizer tray, since they are heavy and tend to roll. A sheet of paper laid in the bottom of a compartment, traced around each item, makes a quick template for a layout.
Finishing
Sand all the edges so they are smooth, particularly the top of the dividers where your fingers will go. A light coat of clear finish makes it easier to wipe up oil and prevents wood from absorbing moisture. If you apply any finish, let it dry fully before loading the tray, and dispose of used rags as the label directs. Labels on the tray bottoms or dividers help everyone find things. Good tool labeling saves time when the organizer is in daily use.
Keep it flexible
An insert is meant to change. Start with simple dividers, put the tray into use for a couple of weeks, and then rearrange. Make notes about what you keep digging for and what never gets touched. If a particular compartment overflows, enlarge it. If another never gets used, merge it into its neighbor. You can then build a second tray to stack on the first, using the same technique, if you find the space and the weight acceptable.