That sounds right, the chain slings at the frame plant all had a tag that could be looked up.

Having said that, We used shop built lifting lugs that were never actually tested, but the design was probably from Our engineering dept.

I have no doubts this forklift will end up with its rear end off the ground or pin will bend..
if, as you say, lifting device is used to lift something else (a solid object?) -or something else may break, that I
have not ever welded or been responsible for
So I need to be aware of what my work was required to achieve and carefully
distance myself from failed attempt of young fellow or any other previous (or latter, if any) attempts
by someone else who tried to add/take away anything from this machine's attachment
Because of all this now, I'm reluctant to issue any written statements unless my lawyer agrees with it
"Safety factor is influenced by how device is used" -and that itself needs to be considered very carefully-I hear ya
--Thanks a lot, Al

I always overbuild/overkill so that in worse case scenario, my welds will endure/fail not
Job must be done in such a way that whomever stands next to it when complete-can not do anything more to improve it
This gives me peace of mind. Being aware all sorts of failures put there I can also design structure to fail where I want it to fail, 
in those situations where too strong is not best either..yes carpet roll can be large.
So forklift' rear end will lose traction, perhaps may go airborne and can become - dangerously- useless
With knife one can slice bread or kill someone. I can only guarantee my (part of) work
There's danger that someone else did work before/after. Liability should accordingly, be limited.
How do professionals gauge who did what? I took several photos and have a witness(es)
Thanks, Blaster

In the event of an accident, the courts will be happy to sort out who is responsible for what.

With that in mind, if a piece of machinery is modified by a third party without the manufacturer's knowledge, the manufacturer is pretty well off the hook. The third party, even if they are following the owner's instruction, will assume a good portion of the liability.

I'm no lawyer and I make no claim to be one, however, I have been involved in several investigations on behalf of the plaintiffs seeking damages. There are a few things to consider:

1) An employee that is hurt cannot sue the employer if he is covered by workers compensation insurance unless the employer does something way off base.
2) Someone is going to pay for the injured employee that is out of work. If the worker is covered by workers comp, the insurance company may become the plaintiff.
3) The third party responsible for the work is the most likely entity that will become the defendant in any proceedings.
4) A defense of "I only did what the owner asked me to do." holds very little sway. Even if the part you fabricated didn't fail, your modification wasn't approved by the manufacturer and may have changed the stability of the machine, changed the lifting capacity, or changed the center of gravity. There are a number of things the lawyer, with his cadre of experts, will bring to the attention of the courts.

Any modification to equipment that lifts loads, especially over the heads of people working with them, is very dicey in the best of circumstances. Even if the machine doesn't result in a personal injury, an OSHA visit can result in very heavy fines if a Professional Engineer was not involved in the modification and there is no evidence of a load test.

Best regards - Al