Here is a question that I answered recently over at Yahoo! Answers:

i recently moved into my mothers house to assist her after my fathers death. i noticed that there was no mezuzahs on any of the door posts.our front door is strange and a mezuzah can only be placed vertical with no room for a inward slant as i had in Miami Beach.can a mezuzah be left vertical on the right side of the door.also…my mother does not want mezuzahs in the house. it is her home.i should be lucky for the outside doors.at 82 years of age she is unwilling to make changes like a kosher kitchen,all door post mezuzahs and now she wants to go to a nearby church because our only temple closed as over the years the majority of jews have relocated.[a church] i asked her.?..i think its more for socialization.maybe the mezuzah might help our home with these dilemma’s.

Here is what I answered:

I am a certified Torah scribe. I write, check and sell Mezuzahs, Tefillin, Torahs etc.

There are several issues involved in your question. First, there is not obligation at all to put the Mezuzah up slanting in. This is only a custom and only for Ashkenazi Jews. This custom is because there are two opinions about how a Mezuzah is to be affixed. One is that the Mezuzah should be vertical and the other is that it should be horizontal. The majority opinion is that it should be vertical, but some have the custom to slant it a bit just to acknowledge the opinion that it should be horizontal.

Regarding the issue of your mother not wanting to put up Mezuzahs. Technically it is your mother’s house and therefore you are only obligated to put a Mezuzah on the door to the bedroom where you sleep. Someone here said that since you are obligated in honoring your mother that you shouldn’t make an issue out of putting up Mezuzahs. I disagree. If your mother was physically ill and didn’t want to take her medication, it would not be honoring her by doing nothing. Spiritual matters are no less important than physical matters.

I would suggest that you think of a way to convince your mother to put up Mezuzahs in the entire house, or at least on as many doors as possible. Perhaps it would be helpful to sit down with her at the computer and look at decorative Mezuzah covers that she would like. Offer to buy for her whichever one she likes as a gift. You know your mother. You are the biggest expert in the world at how to get what you want out of her. You have been doing it since the day you were born. This case is no different, except that what you want in this case is good for her also.

The Mishna in Ethics of our Fathers states, “A Mitzvah brings another Mitzvah”. Perhaps the Mitzvah of putting up proper Kosher Mezuzahs will have a positive effect on your mother regarding the other issue that you wrote about.

Good luck

PS I am going to take this opportunity to shamelessly plug my website if you need a place to buy a Kosher Mezuzah.

http://www.thegreatshofar.com/

I was happy to see the following response:

thank you so much..i appreciate you taking the time to write that information.it has helped so much.i enjoyed your web site and will definitely use it!