Measure the diameter of a leaky heater hose on your car without taking it off and
letting it drip. Then get a new hose the correct size. Take off the old hose, and immediately install the new one.
When making changes to the copper pipe in your house, measure the outside diameter of the existing pipe, so you can buy the right size. Then you will have all the right sizes when you shut off your water, and start working. You won’t be interrupted by a hasty trip to the store.
Does your boat need a new hose, and you don’t want to remove the old one until you have the right size replacement beside you? Just measure the outside diameter (OD) of the old one, and match it to the new one.
A pipe diameter tape measure is quick and easy to use. If you ever need to do any repair work like this, you definitely need an OD tape (diameter tape).