Choosing the right size or length ladder is just as important as the style. One of the most common and potentially dangerous ladder selection mistakes is purchasing a ladder which is either too short or too long.Extension ladders should be 7 to 10 feet longer than the highest support or contact point, which may be the wall or roof line. This will allow enough length for proper set up, overlap of ladder sections, height restrictions of the highest standing level, and whereappropriate, the extension of the ladder above the roof line. The highest standing level is four rungs down from the top. Never stand on the ladder above the support points or roof line.The highest permitted standing level on a stepladder is two stepsdown from the top. A person standing or sitting higher may lose their balance and fall. A person’s maximum safe reaching height isapproximately 4’ higher than the height of the ladder. For example, a typical person can safely reach an 8’ ceiling on a 4’ ladder.