Final answer:
Manufacturers advise using the 4 to 1 rule for ladder placement and ensuring three points of contact for optimal safety when using a portable ladder.
Step-by-step explanation:
According to manufacturers, the easiest and most accurate way to use a portable ladder for safety is to follow the 4 to 1 rule for ladder placement. This means that for every four feet of height you need to climb, the base of the ladder should be one foot away from the wall or surface it's leaning against. Additionally, it's vital to ensure the ladder is on a stable and level surface to prevent slipping or tipping. Ladder safety guidelines also recommend maintaining three points of contact with the ladder at all times—either two feet and one hand, or two hands and one foot—as this helps to maintain balance and reduce the risk of falls.