How can you build a model of tetrahedral coordination from objects found at home? Our college is switching to teaching online mid-semester in hopes of slowing the spread of Covid-19. All the molecular model kits are still on campus. How could you build a model of tetrahedral coordination (say methane) from materials found at home?

I'm aware of computer visualizations (and will make those available), but I think having a physical model when first encountering three-dimensional structures adds value. I made a model from lawn toys (see below), but these are not common household items.
Inflate balloons, and tie them «at their stem» like a bouquet of flowers.  If you take four of them, not too much inflated, you well demonstrate a situation close to $sp^3$ hybridization. These models equally work well in larger lecture halls by the way, and intentionally using different colors allows many options.



(source)



(screen photo

You need some worked examples?  See videos like this or this.

You need a scientific paper? Well, there are as well, e.g., this (open access) expanding the picture to extended $\pi$-systems: