This is a 100mmx240mm (3.9"x8.6") modular storage box/rack/caddy with an optional carrying handle.

The pieces all assemble by press-fit, no tools are required. The parts all print with zero-tolerance fit so that they will hold securely together and this may be used for actual medium-duty work. If you have a small amount of overextrusion some pliers or channel locks may be helpful to provide that extra bit of force to squeeze the parts together.

The basic box design consists of two 7mm thick faces, a 5mm thick bottom, and two 2mm thick walls all in a hex pattern for strength while being efficient with material usage. Assembly is simple.

The optional handle should be assembled in order of the pictures. Note that the grip part of the handle prints with some very small supports, if they remain on your build plate when removing the parts don't worry, nothing peeled off that wasn't supposed to.

To assemble the handle, first press the grip ends through the two faces until the small channel for the retaining clips is all the way through, ensuring the hollow portion of the handle is pointing downward and that the recesses in the handle faces point inwards so they can be clipped to the rack properly.

Insert the retaining clips into the clip recesses on either end of the handle.

You will note that I snapped the very tips off of the handle pictured. I did this while disassembling it after I had already built it once, in order to build it again while taking these pictures. If it happens to you too, snapping off the tip does not affect the functionality of the retaining clips or the clip recess in the handle.

Once assembled, attach the carrying handle to the rack using the joining plugs. This can be a little finicky, it is probably easiest to insert them fully into either the handle or the rack first, and then join the rack and handle together afterward, rather than lining up the empty slots for the plugs freehand and trying to insert the plugs into both parts at the same time.

To test for strength, I put two screwdrivers, two claw hammers, channel locks, pliers, snips, and an 18" pipe wrench in the rack and the handle and rack lifted them without issue even on the basic two wall-loop printing profile. For more strength you could always print with more wall loops, solid joining plugs, or even sub the 2mm thick wall pieces for two more of the 5mm thick bottom piece instead.

Make it double wide with two additional faces, one bottom, and four joining plugs. The handle is designed so it can mount across two faces as shown in the last picture.

Make it double tall, make it whatever you want. I hope you find this useful!