Wrecking yards (also known as scrapyards or junkyards) are common in Knox Country, and are the last resting place for vehicles that are no longer wanted or even usable. Whilst their contents are often low quality or in poor condition (sometimes being little more than burnt-out wrecks), they are a potential source of spare parts and offer expendable vehicles for training up the Mechanics skill.
As a structure, wrecking yards typically consist of an office (usually little more than a parked trailer) with a few filing cabinets and maybe a few odds and ends, and whilst vehicles found in wrecking yards can occasionally be in decent condition they rarely have keys or gas, so they shouldn't be considered a good source of supplies or vehicles for an emergency getaway.
On the Map Project, wrecking yards can easily be identified as they are usually mid-to-large size sand or gravel lots with a chainlink fence around them, a small office, a portable toilet, and no other contents, as the vehicle spawns themselves are randomized.
Like the Louisville wrecking yard, the impound lot in Riverside is a great place to practice your Mechanics skill. The vehicles themselves are almost always in poor condition with no keys or gas, however the value is in the parts. You gain skill even from failing to repair or dismantle car parts, so repeatedly destroying these already mostly destroyed vehicles is a great way to train your skills without obliterating a vehicle you might want to actually use later.