A different "Awkward" T-tongue + loose groove joint

I was asked to assemble a purchased acrylic box which basically is a first-in-first-out stack for frozen surplus breast milk pouches. It´s supposed to live in the freezer, where you place zip lock bags with milk to freeze on the top metal plate. Once frozen the bag is labelled and deposited into the top slot into the stack where they pile up. When a pouch is needed you remove it from the bottom slot, where the oldest deposit resides.

I said, “I can do that. I design, cut and assemble precision kerf adjusted press fit tongue and groove acrylic constructs all the time” and started trying to assemble the contraption, but to my surprise I discovered that the tongues were T shaped and larger than necessary, and, and the grooves were also excessively larger than necessary.

There was no way that the rectangular box was going to stay firm and keep its shape with so much play in the joints.

As an old teacher used to say “When all else fails, read the instruction manual”.

The instructions revealed that instead of using flush precision kerf adjusted press fit joints, the design calls for awkward T shaped tongues that pass through excessively large grooves over which you need to loop an elastic white viton ring that snugly holds the joint in place but allows flexibility. (never mind that you risk poking someone in the eye when the ring flings into oblivion as you miss trying to hook them around the T shaped tab. No wonder they provide twice the necessary rings called for in the design.)

My question to my fellow glowfriend are:

  • Have you seen this type of assembly before?
  • Is this an anti-minimalist design at play here?
  • Am I missing something here? Why would they go to such an elaborate and roundabout way to design the assembly of something so simple? Maybe the freezer factor requires this flexibility in the joints to avoid cracks and breakage?
  • Is there any other reason you may think they used this type of joint? I am always willing to learn new things.


Possibly, if it compresses when cold a tight finger joint could suddenly be loose. I’ve had no problem with the box I built for the fridge, but that’s ~30º warmer so…

The rubber bands literally give wiggle room!


That would be my guess. Is the thing sturdier than it looks?


I can see that overall it puts a lot less stress on everything, means you don’t need a precision cut and can be taken apart again by removing the bands.

I can see that would be really useful when you’ve got materials with very variable thickness.

Actually I quite like it.

Anything you want to collapse frequently this would work for really well.


Yes. I’ve seen it with cheap mdf office organizers sold at daiso. I’m assuming for what i saw, it was a cheap way of not having to be exact. It also makes it easy for people to assemble without much difficulty.

The rubber bands on these are under or behind, so you can’t see them while they sit on the desk. And they make the organizers feel really sturdy because the bands are so tight.


I can see this type of construction being useful for inexact material specs as mentioned above as well as to keep product breakage, and subsequent returns/bad reviews, down during assembly. Acrylic is notoriously brittle with tight kerf specs.


It´s rather strudy, yet yields to deformation without cracking or breaking.


This German shop used the same types of joints for a variety of cool products, from desk organizers to furniture:


Seems like a good idea for something to be taken apart, sanitized, and reassembled regularly.


Can they do that for people too?


It’s actually a pretty elegant design and I like the idea. There will be a LOT of stress put on any of the joints due to expansion/contraction of the material because of the temperature changes. It also reduces stress at the points of contact. I’ve got to remember this one.


@linefeed, Initially I thought it was a sloppy roundabout way to assemble, but I´m glad I shared in the community and we al colectively learned something new.


Pretty close on the ‘Sanitize’

If you know, you know.


And wish you didn’t.


My guess is it’s a solution to avoid gluing while maintaining a snug fit?


I like the concept of the item itself. It’s not fun to dig through a surplus of frozen bags (if you are fortunate enough to have a surplus!) lol :smiley: I’m thankful to be past that phase of life.


I first ran across this in one of the Mark Rober crunchlab boxes, it is a fast way to assemble without tools but definitely takes some getting used to. I flung a lot of rings too.


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