Source: 

OBAR BIDS – Acronym for Opponents Bid And Raise – Balance In Direct Seat.  Popularized by Larry Cohen in “To Bid Or Not To Bid: The Law of Total Tricks“. Conceptually, when one side discovers a trump fit at the 2 level trump (beneath 2 Spades), the other side should consider entering the auction – even bidding without substantive values in direct seat.  While many might make a bid in the balancing/passout seat (“borrowing partner’s King”), making a freebid in direct seat is typically viewed as showing additional values – no so playing OBAR BIDS.

Criteria to consider when making an OBAR BIDS:

1. Sensitive to Vulnerability  – caution when unfavorable “Red versus White”
2. Shortage in OBAR suit
3. Reasonable length in higher ranking suit
4. Working values – honors in higher ranking and side suits
5. Quality of hand – controls, primary honors, intermediate values, sequences, etc

Example:

P – (1Heart Suit) – P – (2Heart Suit);

2Spade Suit                           A reasonable bid holding:

 

Spade Suit K Q J 8 2              Nice sequence, working values, and good lead direction
Heart Suit 5 3
Diamond Suit J 10 5
club suit 9 6 4