There's a shelving slotting system that goes by either the name rivet rack or teardrop rack. I have a shelf that exposes them outward, and figured I could get some use from them by making utilities that interlock with them.

Demo video at https://youtu.be/VF9v49x1sic

An interlocking platform was designed that vertically hooks into two keyholes for stability and features a plug that prevents the things from being accidentally lifted out. The plug is connected by a flat-ribbox flexure, which moves in a constrained way when the utilities are lifted up and down. But to be inserted/removed, they must be pushed inwards/outwards, which can only be done manually with intentional manipulation.

I'm not sure if there's a teardrop rack standard that all shelving systems comply with, but these are compatible with multiple shelves I have from different manufacturers.

Printing

The models can be printed with a brim if needed, but it's recommended not to use one unless necessary. This is because separating the brim from the flexure can be tricky. Organic supports should be used to support the bottom of the higher-printed teardrop key. All models should be oriented correctly so that the correct side is facing the print bed.

The Headphones holder was printed with supports over the build plate and required some post-work to ensure the surface finish was smooth enough not to damage the headphone headband.

Usage

Place keys into the racking; the keying should make it clear which orientation it should be inserted in. After fitting the keys in, make sure the object is fully lowered so it interlocks with the racking. Fit the plug into the keyhole.

Variations

Nail Hook Short/Med/Long

Used to hold stuff that could usually be hooked onto the head of a nail. Comes in 3 lengths; use the shortest length you can get away with. IMO, the short one is great for easy and visible access and stowage of tape measures.

Hook Shallow/Med/Deep

Some hooks. Honestly, it may not be the best design for general hooks, as a hook printed lying on the bed would be stronger, but all things in this project are made using the same keying platform, which requires printing upside-down and upwards, off the bed.

Glasses (2)

For holding safety glasses. Comes in two variations, with the 2 version offering extra support for the front of the glasses. More work can be done with this design to hold safety glasses better, but I'm not sure if there's a universal design that fits all/most safety glasses' shapes. It holds them loosely, so if you bump into them while rummaging through the shelving, you can easily knock them over.

Headphones

For holding hearing protection headphones.
The dimensions need to be adjusted to better fit headphones, and for less 3D printing overhang issues.

EarPlugBox

Holds a small box of earplugs. Unsure if earplugs come in a standardized box size, but this is sized to be box I had on-hand.

Notes

IMO, the short nail hook is pretty effective at holding tape measures, and the earplug box shelf is nice too. The others are alright, but may not be ready for prime-time usage. But I timeboxed this project, so I'm out of time for iterating of stuff ATM of writing this.