In the United States, work baskets/cages/platforms must be approved for use by the forklift manufacturer on all forklift(s) on which these devices will be used.

OSHA 1910.178(a)(4)
"Modifications and additions which affect capacity and safe operation shall not be performed by the customer or user without manufacturers prior written approval. Capacity, operation, and maintenance instruction plates, tags, or decals shall be changed accordingly."

(Note: Some forklift manufacturers will not authorize the use of work platforms on forklifts due to the liability involved.)

OSHA 1910.178(a)(5)
"If the truck is equipped with front-end attachments other than factory installed attachments, the user shall request that the truck be marked to identify the attachments and show the approximate weight of the truck and attachment combination at maximum elevation with load laterally centered."

OSHA Interpretation (November 27, 2001)

"If the manufacturer's operator manual states that a forklift is not to be used for elevating personnel platforms, use of the equipment to support such a platform would violate this provision. Consequently, OSHA prohibits the use of such equipment to elevate personnel. If the owner's manual for the equipment is silent on whether the equipment may be used to elevate personnel, the employer must determine if the forklift was designed for such purposes. The standard places the obligation on the employer to ensure that this type of equipment is used to elevate personnel only where the manufacturer has designed it to do so. The employer would either have to find out from the manufacturer that it was designed for this use or (where that information is unavailable) obtain a certification by a registered professional engineer that the equipment was so designed."

(This interpretation was in response to a rough terrain forklift question but is applicable to all forklifts.)