Demons have a hard time coming thr the doors at Nana's.
My grandgirl a couple yrs ago asked me, "Nana why to you have finger print crosses on all your mirrors"?
I did not tell her so as not to scare her.
Monkey Works has some good advice on how to cleanse your home to keep the evils out.
If you think demons are not real perhaps you might want to rethink this.

what is a finger print cross? does it need to be that specific type?

Nana blesses my house with holy water and the cross on the mirror is from the holy water on my finger.
I order it from the Jordan River and then I also go thro the blessing the water myself as well just in case someone decided to rip ppl off.
You can find some wonderful water and home blessing prayers online.