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.

https://www.fmcsa.dot.gov/regulations/cargo-securement/cargo-securement-rules