He does not open doors, though! When we're gone, he's good in the house for about 5 -6 hours before he even thinks about peeing; longer than that, he has a nice outdoor pen.
I highly recommend dogs for security. Very few malefactors will risk the alarm or possible attack from a dog if they can just go down the street where there isn't one.
A girl, for example, with a nice trained guard-dog breed, even terrier-sized, can walk or jog in safety anywhere; the type of people who will accost or assault a woman in public are generally the type who soil their tracksuits if a dog shows their teeth at them ....