I know this has never happened to you but have you ever found Insurance coverage to be confusing? When you begin with the basic premise that there is NO POLICY that covers everything then things will start fitting together.
If you work on motorcycles, autos, RV's in any capacity then you know you need garage liability coverage. This fine piece protects your assets against a claim. Imagine you are taking a test drive in one of your client's vehicles to make sure everything feels, sounds and works that way it is supposed to and you hit a Yugo. The Garage Liability policy covers the Yugo and other driver BUT there is an exclusion in the policy (remember insurance policies do not cover everything. The care you were driving is Excluded from the coverage because it is not your vehicle. Your GARAGE KEEPERS policy will cover vehicles that are in your card, custody and control. This is NOT covered in your garage liability policy. You need a separate policy for this coverage, or your client may soon own your business if you do not have the money to self-insured for this "peril". Now to make this more fun, you can get a Garage Keeper policy that will pay for what you legally have to cover (Legal liability, Cheap, etc…) or one that covers if the shop has been negligent and legal liability (Direct Primary, OK, this is an insurance term so it does not have to make sense unless you work in Insurance, Hence the explanation of what this does). This is much better coverage than the legal liability or if you want a plan that will pay for everything, no questions asked, you get Direct Excess coverage (best). So if the client does not have sufficient coverage on their vehicle, this will pay for getting it fixed. This fills in the gaps for your client.
Guess What? There are different price levels. Surprise! So how much of a risk taker are you? You can assume all the risk and pay for everything yourself (self-insured), get coverage for what you legally must cover, get coverage that covers your negligence and what you legally have to cover, or get Direct Excess and not worry about having an incident because you are covered.
Remember saving 15% could cost you 100% of everything.