Check the average length of the letters in the publication you are considering if they don't state it in their guidelines. (relevantmagazine.com)
The overall length of the letter must be kept short, since most potential employers do not have the time to read through irrelevant details. (coverlettersandresume.com)
Cut the tape with a Xacto knife in strips that run the length of the letter and apply the sticky side to the back of the letter. (pbteen.com)