Definately get a lock, if your yorkie got out, you probably wouldn't see her again, most people wouldn't put up a "found dog poster" for a tiny cute yorkie, they would keep her (or worse
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I have a lock on mine in the front so this can't happen, If my electric guy needs to see the meter and he can't see it, he has to knock on my door for me to let him in. If I didn't have a lock he would open it, so would our neighbor's kids when their ball goes in our yard. We have a big piece of property with several gates and every now and then, my husband forgets to shut one all the way. One time I couldn't find Tinkerbell and I was going crazy with worry, I found her out in our very back property chasing our ducks. She was having a blast but it was very dangerous because we have a neighbor with 3 big dogs, including a pitbull, if she ever got out our old country fence out back there, she would be eaten alive. I about killed my husband when I found her out there, and now that she's done it, she keeps trying to figure how she can get out there again, the little brat! As long as that gate is locked she can't get out, but it scared the crap out of me!