Federal regulations do not require full skirts, only 8" (203mm) bevel toe guards, which are standard on pit mounted dock lifts. If personnel protection is desired beyond that required by federal regulations, use electric toe guards.
Fabric roller shades and accordion bellows skirting are not durable and because they do not provide a rigid physical barrier, their protection is based upon the notion that "what you can't see can't hurt you."
Telescoping sheet metal skirt sections are more rigid, but are very susceptible to damage which makes them inoperable.