Ramrod straight/(as) straight as a ramrod American British informal
To describe someone who stands or sits straight, usually attached with a formal or professional manner.
My boss reminded me to sit ramrod straight at congratulation party, for this manner partly built trust in partners about our project.
The teacher required all students to stand as straight as a ramrod to take a picture.
The bodyguards stood straight as a ramrod in front of the hotel to escort the president.
Daughter: So I really want all my friends to have a great time. I was thinking it would be a good idea to have some candy out on the tables for people to snack on.
Mother: Well, if you want them to really enjoy themselves, candy is dandy but liquor is quicker.