This is the time of year when most homeowners spend a good deal of time mowing and trimming the lawn, pruning trees and shrubs, trimming hedges, and doing many other chores that involve working with power-driven lawn mowers, edgers, trimmers and similar pieces of motor-driven yard equipment. These tools go a long way toward transforming drudgery into a pleasant outdoor chore, but they can also cause serious injury if carelessly treated or not properly handled by someone unfamiliar with safe operating practices.

Probably the most important safety rule to follow when using any power-driven tool or appliance is to read the operating manual carefully and be sure you understand it. Many accidents occur because of simple ignorance -- not knowing how to use the machine properly. The user should be thoroughly familiar with what its various controls and adjustments are for, and with how they can be changed or regulated when necessary.

Equally important is knowing how to keep the tool in proper working order, what to do when minor problems develop. Regular preventive maintanence -- lubrication, sharpening, adjusting of drive belts, replacing of worn parts and similar care -- is just as important for safety reasons as it is for proper operating efficiency, because a properly maintained yard machine is less likely to cause accidents due to forcing or overloading, or due to something letting go or falling off while the tool is in use.

Tools powered by a gasoline engine require extra care to protect against fire or explosion while pouring fuel or refilling the tank. Make sure the gasoline is stored in an approved container outside the house, and in a place where children cannot get at it. Never refuel when there are flames or lit cigarettes nearby, and do your filling on a paved area where spills can be easily washed away. Try to avoid overflowing the tank when you fill, but if you do spill some, wipe up the excess before starting the engine.

Users of electrically powered mowers, trimmers and other tools do not have to worry about gasoline, but they must take extra precautions to avoid damage to the long extension cords often used with these tools. In addition, they should avoid using them when the ground is wet. Clippers or trimmers should never be used on wet foliage or plants. If the tool is not double insulated and has a three-prong grounded plug, make sure any extension cords are also three-conductor cords with grounded plugs at each end.

Power mowers are probably the most widely used of all outdoor power tools, and they are probably responsible for more accidents than any others piece of equipment around the house. A few of those accidents are undoubtedly due to faulty design or poor construction, but most accidents occur because of ignorance or carelessness. Here are some rules every operator of a rotary power mower should keep in mind:

1. Before using a power mower make sure the blade is clean and properly sharpened: A dull blade is not only harder on the grass, it is also more likely to "throw" things out the chute. Also, make sure all bolts, screws and other fasteners are tight.

2. Clear the lawn area of stones, twigs, wire and other debris, and make sure the discharge bag is connected, or that the discharge chute has its deflector plate in position. If the machine has a washout port, keep this closed while cutting.

3. Never walk behind a power mower with bare feet, and make sure there are no children or pets close by when cutting.

4. Don't make adjustments to cutting height or try to make minor repairs while the engine is running. Don't try to clean out the discharge chute or unclog it while the engine is running.

5. Stop the engine when crossing gravel paths, walks or roads, and stop it before emptying the grass bag.

6. When mowing slopes, work from side to side across the face of the slope. If you push the mower up and then pull it down the slope toward you there is a danger of the mower alternately "running away" from you, or running down onto you. With a riding mower the rule is exactly opposite: Riding up and down a slope is much safer than riding across the face of it because of the danger of tipping or rolling over.

7. When you have to make repairs or clean out the underside of the blade housing, wait until the blade has stopped spinning completely, then disconnect the spark plug wire to play safe. If you must run the engine, do not do, it indoors, and disconnect drive belts or chains to keep the blade from rotating.

8. Never leave the engine running when you step away from the mower or leave it unattended, even if the clutch is disengaged. Even if you turn your back on it for a few moments, children, pets, or even another adult could accidentally walk into it, or start it up by engaging the clutch.

Power mowers are not the only outdoor power tools used around the home, or that can cause accidents if carelessly handled. Other frequently used yard tools such as hedge trimmers, lawn edgers and string trimmers must be handled with caution to avoid accidents. Aside from the cautions mentioned above that apply to all gasoline or electric-powered tools, here are a number of other precautions that should be kept in mind when using these tools:

1. Never hold or carry a hedge trimmer by grabbing the cutting blades; aside from the fact that the blades are sharp enough to cause a cut, there is also the possibility that the motor could be started accidentally and there could be serious injury.

2. When using electric clippers, trimmers or edgers, make certain the cord is in no danger of being cut or damaged by the blades. Drape the cord over your shoulder so it comes from behind, rather than from in front of you.

3. A string trimmer should be operated only when its head is down near ground level, never while being held in the air. Keep others persons a safe distance away and hold the tool in such a way that its spinning head (whriling string) is angled slightly to the left; this way, trimmings will be thrown away from you as you work.