I believe you're referring to a kickstand.
They are stabilisers or stabiliser wheels inBrE.
This thread just made me think of a new insult - 'as useful as a kickstand on a tricycle'.
It could be used to reference somebody's value, or their contribution to a project, etc.
I suppose it could also refer to redundancy or pointlessness - 'as necessary as a tricycle kickstand'
Wear short sleeves! Support your right to bare arms!