goes above the door knob.

It depends on the locks that you have.
I've been used to above the knob, however our multi point French doors require that the thumbturn be below the knob.

In a mortise set the thumb turn would be part of the whole unit so a carpenter would not have a choice.

This is a separate thing from the knob. We are doing these on some doors for privacy.

Interior privacy I would probably go with beneath the knob. I was thinking of exterior like a deadbolt when I said above.

If you mean a mortise privacy bolt with a thumb turn as linked below, it should go above the latching hardware for easy use.

This is not a "latch"; it is a manual locking bolt and is not considered "privacy" hardware because it cannot be unlocked from the other side with a tool in an emergency. You should not put one on a child's door or a bathroom.

Here is a link that might be useful: mortise privacy bolt with a thumb turn

Here is a thumbturn deadbolt lock with an emergency release button.

Here is a link that might be useful: thumbturn bolt w/ emergency release

ours looks similar to the first one you posted, Renovator, and the hardware company said you can open it from the exterior. the hardware company said it should go below the interior knobs so it doesn't look like a deadbolt.

i believe athensmom said she has these on her kids doors and you can get in from the outside.

It IS a dead bolt so if that is something you don't want to see your decision has already been made. I would put it where I could see if it was locked or unlocked.

Ours is above the door knob. I think it would be hard to see/use if it was below. Ours you can get in from the outside. There is a brass panel that snaps off if you get a fingernail under it.

Here are ours:

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We have a small knob and rosette. If your knob is larger or you have a larger backplate I would definitely do above the knob.

Classically above the knob, with no access from outside the room.

And we all survived hundreds of years that way.

Interior doors are not all that solid, and the bolt throw barely makes it into the door casing.

The are easily broken through in an emergency

Thanks for the photo, athensmom. What are your doors made of?

They are MDF solid core, not molded but stile and rail construction, with wood stiles. They are made by Masionite but are not their more common "molded" MDF door. These are like the Trustile doors we looked at but quite a bit less.

The stipling you see is from the paint roller. I hate that but it is very unnoticable if you are more than 6" away. I wish I had asked them to use foam rollers instead or to brush paint it but oh well. . . I figure we will repaint the doors eventually.

athens, my eyesight isn't good enough to notice the stipling. i think your doors look great. i asked about their material because i heard it was difficult to bore the necessary holes for these thumb latches into solid wood.

Depends on if you mean a thumb latch or as most people have been presuming, a "thumb turn" they are distinct meanings to each types of mechanism.
The deadbolt cylinder part is always above the exterior thumb latch on mortise locks that utilize them.
Casey