I played a 4-player game of Deck Building tonight with some new players and some questions came up.
Suppose you have 4 screws in your hand. You buy a card that costs 4 screws. Clearly you cannot buy another card. But can you still build a card from your hand? The rule book does not say otherwise, so we've been playing that you can.
A question came up about what stairs were worth for purchasing other cards. Re-checking the rule book now, I see that it does mention that stairs are not worth any screws.