Straight from the FMCSA:
Minimum Number of Tiedowns
The cargo securement system used to restrain articles against movement must meet requirements concerning the minimum number of tiedowns. This requirement is in addition to complying with rules concerning the minimum working load limit. When an article of cargo is not blocked or positioned to prevent movement in the forward direction, the number of tiedowns needed depends on the length and weight of the articles. There must be - one tiedown for articles 5 ft or less in length, and 1,100 lbs or less in weight; two tiedowns if the article is -
5 ft or less in length and more than 1,100 lbs in weight; or
greater than 5 ft but less than 10 ft, regardless of weight.
In the following example, one tiedown is required because the article of cargo is 5 ft in length and does not exceed 1,100 lbs. If the article of cargo were greater than 5 ft in length but less than 10 ft, two tiedowns would be needed regardless of the weight. When an article of cargo is not blocked or positioned to prevent movement in the forward direction, and the item is longer than 10 ft in length, then it must be secured by two tiedowns for the first 10 ft of length, and one additional tiedown for every 10 ft of length, or fraction thereof, beyond the first 10 ft. An example of this is provided below. If an article is blocked, braced or immobilized to prevent movement in the forward direction by a headerboard, bulkhead, other articles that are adequately secured, or other appropriate means, it must be secured by at least one tiedown for every 10 ft of article length, or fraction thereof.
- See more at:
https://www.fmcsa.dot.gov/regulation....JAupbU4H.dpuf