Drying clothing and linens on an outdoor clothes line instead of a machine dryer saves energy and money. If you're going to line dry regularly, you'll need to install posts for the line, or a single-post, umbrella-style rotary clothes line. Installing the posts is more involved than simply digging a hole but you can do it in about a half an hour per post, plus drying time.
Dig a hole in the desired location about three times as wide as the post and about 30 to 60 cm (12 to 24 inches) deep. Place post in the hole periodically, until the hole is the right depth. The level of the clothesline should be just over head level.
Pour 15 cm (6 inches) of gravel into the hole while the post stands in it. Spray just enough water in the hole to dampen the soil.
Straighten the post using a level and have someone hold it in place.
Pour rapid setting concrete directly into the hole, filling it to the top. Pour about a cup of water over the concrete. Concrete should set in about 20 minutes.
Wait 4 hours before hanging the line for drying clothes.
Regular concrete can be used instead of rapid-dry. Mix before pouring into the hole and allow at least 24 hours to dry.
If you're not sure whether there are utility lines underground in your garden, call your utility company to check before digging.