After 15 years of being opened and closed, the lock on the door to our bathroom needed replacing. The lock was a standard one that most of the contractors put in the apartments that they build. It wasn't totally shot, but sometimes you could lock the door and then have a hard time openning it up again.
I had no idea how how to change the lock. I wasn't born with two left hands, mind you. I guess there are other things that just interest me more. The troublesome lock remained in place, much to the chagrin of those who would find themselves temporarily locked in the bathroom.
Another unrelated problem that I had was copying keys to the apartment. It happened more than once that the keys that I had copied at a hardware store did not work when I came home to try them out. The people at the hardware store did not know how to copy keys well, or they just didn't care to do the work properly.
Both of my problems were solved when I found a fantastic hardware store in the Har Nof neighborhood in Jerusalem. The store is called "HaKol LaBayit" (Everything For The Home), and is run by American immigrants. I had some keys copied there and when I returned home they actually worked. The next time I was in the area, I entered the store and told them about my problem with the bathroom door. They showed me the part I needed to buy, and told me how to put it in. When I came home, I tried unsuccessfully to take the old lock out. I called "HaKol LaBayit" on the phone, and the lady (!) there explained to me how to take the lock out. (You have to remove the door handles first. In order to remove the handles there is a little pin holding the handles in place that has to be pulled up and out. Afterwards, after removing two screws, the mechanism can be removed.)
An old Jewish joke says that a man should have three things: A good doctor, a good lawyer, and good children...but that he shouldn't need any of them. I add to the list "a good hardware store".