Questions & Answers about Vodítko je u dveří.
Because the subject is vodítko, which is singular.
- vodítko = one leash / lead
- je = is (3rd person singular of být, to be)
- jsou would be are, used with a plural subject
So:
- Vodítko je u dveří. = The leash is by the door.
- Vodítka jsou u dveří. = The leashes are by the door.
The preposition u usually means by, at, near, or next to, depending on context.
In this sentence, u dveří means something like:
- by the door
- at the door
- near the door
It does not necessarily mean the leash is touching the door. It just places it in that area.
A very important grammar point: u takes the genitive case.
So after u, the noun has to be in the genitive:
- dveře → dveří