There is an unspoken rule in Boston regarding shoveling a street parking spot - if you shovel the spot, it is yours. These claimed spots are typically marked by a folding chair, cone, or recycling bin.
Basically, when you shovel your car out from 24inch of snow to drive to work, you leave a marker in your spot indicating that the spot is yours. No one takes it! Quite an honor system! I first learned about this from my brother who lived in Boston for 4 years before I came to the area. As I was walking around I noticed a bunch of chairs sitting on piles of snow next to parked cars and remember that these are used to mark the spot when the car leaves.
For those visiting during the snowy season... don't park in these spots!!!