These are both Heideggerian terms.
Present-at-hand translates vorhanden and Vorhandenheit. It roughly denotes theoretical knowledge.
Ready-to-hand translates griffbereit, zuhanden and Zuhandenheit. Which denotes roughly practical knowledge.
I find it easy to mix up the two meanings: What is 'present' is also 'ready' to use. Are there alternative translations that make the differences clear. Or is the actual ambiguity intended by Heidegger?