Toy Model

Knick Knacks are toys that can be picked up in Fallout 4, but cannot be salvaged or broken down. These are mostly used to decorate your home, but can be sold for a fair amount of caps. You can build many robot models, ranging in quality, if you're lucky enough to find them.

The standard versions of the robot models, i.e. not the parts models, can occasionally be found at random in the Vault-Tec lunchboxes scattered throughout the game. Clicking on the lunchboxes yields a random small item, either a consumable or a small junk item. There are a number of these lunchboxes scattered throughout the Commonwealth, and each one is another chance to try for one of the five standard robot models. It may take a while, but patience and careful searching can pay off here.

If you attempt to sell any of the models to a vendor, you will receive the message: "You cannot sell quest items". This would seem to suggest that they may be used in a quest somewhere.