And then there are positions where you can't loosen the skewering square but where this isn’t as important as it seems. Where does White have a skewer this time? Of course you see the alignment of Black’s king and queen and so imagine Qa3. It would be easy to dismiss the idea almost immediately because there seems to be no room for your queen; a3 is guarded by Black’s king. But that capture by the king would, among other things, be a forced move (if Black wants to avoid QxQ). Anytime you would lose a piece to the enemy king, ask what the king’s new square would mean to the position. The first way to ask that question as a practical matter is by considering what checks would be possible against the king in its new position—here, on a3. There would be two: Nc4, which Black can escape with Kb4, and Nc2—which is mate! When the enemy king is in traffic, as Black’s king is here, it is especially important to see whether any checks against it may be unexpectedly effective.

Do not dismiss ideas too quickly because they seem not to work. Ask why they would not work, and what the board would look like if they were to fail.