The Rule of 20 is a guideline for deciding whether to open the bidding. It attempts to refine traditional high card point count
by also taking suit length into consideration. The rule is pretty simple: add your high card points
plus the number of cards in your two longest suits. If the total is 20 or more, then the hand is worth an opening bid.
10 HCP + 5 hearts + 5 clubs = 20. Open 1 in accordance with the Rule of 20.
12 HCP + 4 hearts + 3 of any other suit = 19. Pass.
The Rule of 20 was popularized by American expert Marty Bergen in the 1990s.