If you have a small amount of garages, this may be a useful solution for you.
Create a list for each garage
Example List Names:
Create a column for Assigned To (or just rename Title field)
Create a column for Spot (either choice or lookup to your list)
Create a column for Level (either choice or lookup to your list)
Create a sharepoint group for each garage
Example Group Name:
Garage01Managers - Corresponds to Garage01 list
Garage02Managers - Corresponds to Garage02 list
Create a sharepoint group that will have read-only for all garages
Example Group Name: GarageReaders
Break inheritence on each garage list and specify the rights for the following groups
Example for List Garage01
Make Garage01Managers Contribute
Make GarageReaders Read
Remove all other Garage Manager groups from the list
Now you can just add/remove managers for corresponding lists through SharePoint groups. If you need someone to have read-only view of all garages, just add them to the GarageReaders sharepoint group.
Then just have a page that has a link to each Garage.