"spare part" or "spare parts" catalog

[tkean1952]

Good afternoon,

which is correct:

a) spare part catalog
b) spare parts catalog

which is correct:

a) spare part solutions
b) spare parts solutions

I would appreciate the rule or reasoning, too.

This is coming from a german company that creates catalogs, but wishes to name their department "solutions".

Thank you.

[Casiopea]

a) spare part (the catelog is called 'spare part'; it's a coinage)
b) spare parts catalog (The catelog sells spare parts)

a) spare part solutions (again, it's a name, a coinage)
b) spare parts solutions (the solutions refer to spare parts; this isn't a name or a coinage.)

"spare part solutions" is a very cool name for a catelog, and "solutions" is a cool name for a department.