It depends on local laws. In most cities, universities, etc. it is illegal to chain a bike to a handrail, tree, signpost, lamppost, telephone pole, fence, etc. that is on public property. In such a case, a bicycle is required to be locked to a bicycle rack. On private property, where bikes can and cannot be locked up is up to the property owner.
That is the correct spelling of the compound noun "lamppost."
What type of atom or molecule is in lamppost
about 10 ft
Morning glories is not a compound word, but lamppost is a compound word.
Books were not chained.
How does bicycles work
If the bicycles belong to ONE FRIEND, it's "friend's bicycles." If the bicycles belong to TWO OR MORE FRIENDS, it's "friends' bicycles."
There is no specific collective noun for bicycles, in which case a noun suitable for the situation is used, for example a rack of bicycles, a row of bicycles, a standof bicycles, etc.