Q: Expect clean water alone to get the job done most of the time. Save yourself the time and money and use chemical cleaners only when absolutely necessary. Expect these to leave behind streaks and film if you don’t thoroughly rinse them off. Rinsing your roof with water at least once a year should reduce the need for using chemical cleaners. Don’t expect a simple splash of water to accomplish much. Use pressurized water to blast dirt away. For a light job, start by using your garden hose and a wand or spray nozzle attachment and see if its jet setting is strong enough to work. If not, rent or invest in a power washer and use that instead. Avoid stepping directly onto dirt, grime, and debris. Treat any material other than the roof itself as unstable. Before climbing onto or advancing along your roof, use your hose or power washer to clear a path for yourself to reduce the chance of slipping. If you have to first clear a path in order to attach safety lines and other gear to the roof, wait until the washed path has dried before climbing onto the roof. Make washing easier by cleaning the highest points first so the dirty runoff flows over yet-to-cleaned sections. Continue blasting dirt and debris by advancing downward along the roof’s slope while steadily pushing dirt and debris down toward its edge. However: Roof designs vary greatly, so don’t treat this as an absolute must. If your roof is particularly steep and/or has sections well out of reach, always opt for safety and hose it down from a lower, safer point. Don’t rush the job. Opt for a slow and steady approach to ensure safety. Advance along your roof at a safe pace while minding your footing at all times to minimize the risk of slipping.
A: Favor using plain water over chemical cleaners. Use pressure. Clear a path first. Start from the top if possible and blast downward. Work slowly and patiently.

Q: Place 3⁄4 in (1.9 cm) pieces of plywood on the ground. These shoe plates need to be wide enough to support the forms you built. Arrange them so they border the hole in your yard where you plan on pouring concrete for the wall. Before you continue, make sure the shoe plates and forms leave the correct amount of space you need for your wall.  Plant the stakes firmly in the ground. When your forms are in place, they won’t budge at all. Test them out by pushing against them with your hand. If you’re having a hard time getting everything to stay still where you need it, try using wire ties. Wrap wires around the studs in the forms to tie them to the shoe plates. Drill holes in the plates as needed to attach the wires. Make the holes evert 12 in (30 cm) along the length of each stud. Leave about 2 in (5.1 cm) of space between the holes and the studs to avoid damaging your forms. Use 8 gauge wire ties which have a diameter of about 162⁄1000 in (0.41 cm). Basically, you need to cross the wire over itself. Loop it around the wale on 1 side, thread it back through the hole, then loop it around the wale on the other side. The part of the wire between the forms will form an X. The wires hold the forms together when you pour the concrete. If the forms slip out of place, you’ll be looking at a concrete mess instead of a solid wall. Lower the stick towards the center part of the wire. Wrap the wire around itself by turning it with a circular motion. Make sure the wire gets as tight as you can make it. If it feels slack, your forms may slip out of place. Another way to do this is by sliding tie rods through the holes. Slide brackets onto the ends of the rods so they can’t slide out of place. You will need wood blocks as thick as your wall will be. These spacers stay in place through friction. You don’t actually attach them to the wall. They prevent the forms from moving in as you work. Check your local hardware store for spacers. Many places sell “spreader cleats” or a similarly-named product. If you can’t find any, you can always cut them yourself out of scrap boards. Make a 1⁄8 in (0.32 cm) hole all the way through the center of each spreader. When you’re done drilling, string a wire gauge through them all. Loop the wire around the top and bottom spreader. Leave a little extra length on the top part of the wire so you can easily pull the spreaders out later. Set the loop on top of your wall for now. Try tying them to the wall so the wires don’t slip into the concrete as you pour it.
A: Set the forms on plywood boards near where you plan on building the wall. Drill 1⁄8 in (0.32 cm) holes on either side of each stud. Run wires through the holes and tie them to the wales. Tighten the wire tie with a stick or another tool. Slip wood spacers beside each wire. Drill through the spreaders and wire them together.

Q: While this method is less accurate, you can use it when the shadow method won't work, such as on an overcast day. Also, if you have a tape measure with you, you can avoid having to do math. Otherwise, you'll need to find a tape measure later and do some simple multiplication problems. For the most accurate measurement, you should stand so that you are on a piece of ground that is about level with the ground at the tree’s base, not higher or lower. Your view of the tree should be as unobstructed as possible. You can use any small, straight object, such as a paint stick or ruler. Hold it in one hand and stretch your arm out so that the pencil is at arm’s length in front of you (between you and the tree). That is, your friend’s feet should be aligned with the pencil’s tip. He or she should be about the same distance from you as the tree is, not further away or closer toward you. Since, depending on the height of the tree, you may need to be some distance away from your friend, consider using hand signals (with the hand that is not holding the pencil) to tell him or her to go farther, come closer, or move to the left or right. You'll need to measure the length of each mark and the height of your friend, but you can do this after you go home, without having to return to the tree. Scale the difference in lengths on the pencil up to your friend's height. For instance, if the mark showing your friend's height is 2 inches (5 cm) from the tip and the mark for the tree's height is 7 inches (17.5 cm), then the tree is 3.5 times as tall as your friend, since 7 inches / 2 inches = 3.5 (17.5 cm / 5 cm = 3.5). If your friend is 6 feet (180 cm) tall, the tree is 6 x 3.5 = 21 feet tall (180 cm x 3.5 = 630 cm).  Note: If you do have a tape measure with you when you're near the tree, you do not need to do any calculations. Read the step above for "if you have a tape measure" carefully.
A:
Use this method as an alternative to the shadow method. Stand far enough from the tree so you can view the whole tree—top to bottom—without moving your head. Hold a pencil at arm's length. Have your friend move so that you can sight him or her “through” the point of your pencil. Find the answer once you have access to a tape measure.