Adjectival step by step

Question

When used as an adjective, is it step by step or step-by-step?

Example,

Thank you for this step by step guide.

or

Thank you for this step-by-step guide.

Answer 1

According to Wiktionary, step by step is the adverbial form, whereas step-by-step is the adjectivial. So your second example is the correct one.