Banners can be placed on one block and half of it is in the floor

Put the summary of the bug you're having here
Banners
What I expected to happen was...:
Describe what you thought should happen here
you should not be able to plce them on one block it needs to be two
What actually happened was...:
Describe what happened here
i could place it on one block and the half was then in the floor
Steps to Reproduce:
1. Put a step by step guide on how to trigger the bug here
2. ...put a banner one one block whit ''block'' under it
3. ...