Sounding the alarm

When you're about to do anal with someone and you slap your dick imbetween their ass cheeks creating an alarm type noise to notify your partner, you're about to enter their rectum. Can be enhanced by shouting 'bombs away!' Or by screaming like a gibbon

Tyler: "Dude, did you do anal with her?"
Tristan: "Yes but I was sounding the alarm, so all us fine, as she was prepared."
Tyler: "Indubitably...."

Barn doors

Big ol' vagina lips, so big that they may impede upon the pleasure and/or effectiveness of sexual intercourse.

Tristan: "Did you end up getting with that girl?"
Tyler: "Yeah but she had a pair of barn doors, I could barely fit it in and I got rope burn."
Tristan:: "That bitch!"