Many mandolin players use a strap because it allows them to play more easily while standing up. Knowing how to attach the strap is critical because a strap that comes off while you're playing can cause your mandolin to crash to the floor. With a little practice, you'll be able to attach the strap properly every time.
Locate the end of the strap that looks like two laces or strings. Tie this end to the mandolin by threading the laces underneath the strings just past the nut and tying them securely. If you have an "F" style mandolin, you can use this method, or you can tie the laces to the scroll on the top side of the instrument.
Drape the other end of the strap across your shoulder, around your back and back out to your front underneath your picking hand.
Fasten this end of the strap by pushing the tailpin of the mandolin through one of the holes in the strap. Most straps have multiple holes so that you can adjust the length of the strap.
Hold the mandolin in both hands and gently tug downward to see if the strap is secure.
Play the mandolin to see if the height is suitable. Make adjustments to the strap at the tailpin end of the mandolin if necessary.