Yes maybe a boring subject possibly………………. But unless you have a water wheel or mad inventor style pump system how are you going to get your rain water out of your water butt??
Some water butts come with a tap attached and others have a flat area near to the bottom for you to create a hole for a tap. This can easily be drilled and then the hole tidied up with some sand paper. Then you can insert your tap into the hole. Use the nut (supplied) on the inside of the water butt to keep the tap connected securely. Check if your tap fitting is secure on the outside use the washer to make sure the fit is water tight (also supplied).
Now your ready and able to use all that freely collected rain water to feed your garden.
Making sure you have enough room under your tap to fill your watering can! Sounds silly I know but if your not used to getting water from the bottom of your water butt this can be an issue.