How do I put flower pots on my mantel bricked front of house?

move out of that neighborhood!!

Bolt them down....

We had two very large pots painted black potted with red geraniums on our front porch that we knew would be a target for crime so our solution! My Husband put I concrete block in the bottom of each planter and then we filled in with the dirt and plants. Twenty years later we drove by and they are still there.

Could you wire them down to something maybe screw in cement screws then fasten wire to them

Bolt flower box to the brick ledge - try to bolt either into the house ledger if it is where the brick "mantel is" with long concrete anchor bolts and nuts that are permanently glued to the brick underneath the planter if you can't drill the bolts, or have a skilled carpenter attach a ledger board to the house where you want to put the planter(s) and then use carriage bolts to bolt the planter(s) through the ledger board into the house. Don't expect to take the box with you if you move. You can glue down flower pots inside the planter but nothing will prevent the kind of person you're dealing with from ripping the flowers right out of the pot. You can't glue THEM into the pots, unfortunately. This is a plague everywhere, it seems. This short video shows a way to "lock" pots down using a wire cable threaded through the drain hole of a pot and then bolted into concrete or locked with a mini-padlock to a metal spindle on a porch rail. https://www.youtube.com/watch?v=M9mFOben_4E A really bright set of security lights might deter some thieves. And you could try getting video of them on camera. If that is successful, I would contact a local TV station and ask them if they would be interested in running a feature on garden thieves and showing the thieves on your video, asking for help in identifying them. Who knows, the police might actually go after somebody if the thieves are positively identified with such evidence, but as you can imagine, hunting for plant thieves other than perhaps in a rural community where they don't have much more serious crimes to deal with like they do in a larger urban area. I would also introduce myself to other tenants/residents/owners who live around you and ask them if they've had a problem. Neighborhood awareness that there's a problem can be a deterrent in and of itself.

I would also put itching powder all over my plants, pots and planter, and be very careful when watering so you don't get it on you! If you can't stop the theft, at least it would be some degree of payback to the thief!

Can you secure them with thin metal wiring?