Overcalling 1-level openings

When opponent has opened the bidding at 1-level, an overcall can be made based on the following table:

Bid	Meaning	Developments
At 1-level	5+ cards, 8-17 points	"+2 rule" applied, i.e. treat the overcall as an opening bid, but responses which normally shows 6-9 points would now show 8-11 points, and so on.
1NT	Same as 1NT opening Promises stopper in opponent's suit(s)	System ON
Non-jump at 2-level	5+ cards, 10-17 points
Jump to 2-level/3-level	Same as weak opening	System ON
2NT	Unusual 2NT

Remark:  For a hand that is too strong to overall (18+ points), a takeout double can be used instead.