Models are usually assembled from commercial kits (but see below).
Nearly all commercial kits contain basic pamphlets on first aid.
Less frequently a hobbyist will scratchbuild out of economy, as sometimes the raw materials cost more than a packaged commercial kit.
One can sprout broccoli seeds using a jar or a commercial sprouting kit.
They may not be built entirely from a commercial kit.
There are many commercial kits available that will carry out this step using some form of reverse transcriptase.
In recent times, many commercial kits have been created to perform plasmid extraction at various scales, purity, and levels of automation.
A commercial kit for Tn5 transposition is commercially available and is extensively used in post-genomic technologies.
Due to the circuit's simplicity, it forms the basis for many of the learning projects in commercial electronic kits.
Hobbyists may kitbash to create a model of a subject (real or imaginary) for which there is not a commercial kit.