Question

the maximum height at which a scaffold should be placed is 20 feet. tubular welded catenary ladder jack float

Explanation:

Ladder jack scaffolds are one of the types of scaffolds. According to safety standards, the maximum height at which a ladder jack scaffold should be placed is 20 feet. Tubular welded scaffolds, catenary scaffolds, and float scaffolds have different height - related safety requirements and characteristics that are not typically associated with this 20 - foot maximum height limit.

Answer:

Ladder jack