You did it again – locked the door and left your keys behind. Only this time, you want to skip the part where you break the bedroom window to get into your house. A good locksmith can save the day – and your window.

Even more important, a good locksmith can help you be sure you have locks on your doors that will protect you when someone other than you is trying to get into your home.

Bay Area Consumers’ Checkbook Magazine and evaluated 34 locksmiths, collecting customer ratings and prices for a sampling of typical jobs. Fortunately – should you need a locksmith – many firms were rated “superior” for overall performance by more than 80 percent of their surveyed customers.

And, Checkbook found, you needn’t pay more for top-quality service. Checkbook’s researchers – without revealing their affiliation with Checkbook – collected price quotes for carefully specified jobs. Many of the firms rated highest for quality also had low prices – and prices did vary widely. For example:

— To do an emergency lock picking of a key-in-knob lock, prices ranged from a low of $65 to a high of $115, with an average price of $88.

— To install new single-cylinder dead bolts in two doors, prices ranges from $137 to $400, with an average price of $246.

It’s worth it – particularly in nonemergency circumstances – to call around for prices, or to have more than one locksmith come to your home to provide estimates.

Apart from emergencies, it’s worthwhile to review the condition and types of locks in your home. Burglars typically enter homes through relatively crude means-by opening unlocked or poorly secured doors and windows. Before you look into high-tech security, here’s some advice for evaluating your locks:

— Key-in-the-doorknob locks don’t cut it because they usually can be quietly shimmied open in a few seconds. Although a guard plate can prevent this, these are still relatively easy to defeat.

— Exterior hinged doors – including those leading to a garage – should be equipped with good dead bolts.

There are four options for dead bolts: cylinder, interconnected, vertical, and horizontal. Each has its strengths and weaknesses, and a good locksmith can help you choose which type is best for each application.

Be aware that even dead bolts have weaknesses – which, fortunately, can be corrected. For example: some vertical and horizontal dead bolt locks come with puny screws; they should be replaced with the thickest steel screws that fit. Also, most cylinder dead bolts and some interconnected locksets come with 3/4-inch screws to secure the strike to the door frame. Replace these screws with 2- or 3-inch ones. Better still: Replace the regular strike plate with a “security strike” or “strike box” that has holes for additional screws.

And, because cylinders on many locks can be picked, you might consider replacing them with high-security cylinders, which can cost from $80 to $200 or more.