A count signal indicates the number of cards that a defender holds in a given suit. Playing high-low in a suit indicates an even number of cards in that suit, while playing low-high indicates an odd number. Count signals may be used when either partner or declarer leads the suit.
Of the three types of defensive signals, count signals have the second-highest priority:
- Attitude
- Count
- Suit-preference
By default, a signal is for attitude unless it's clear that a count signal (or suit-preference signal) is necessary.
Example: Following Declarer's Lead
Count signals are most commonly used when declarer leads a suit and it's important for the defenders to show count.
For example, suppose partner leads the 
Q against South's 3NT contract:
| | Dummy | | |
|  85 | |
|  J43 | |
| 963 | You |
|  KQJT9 | AJ92 |
| | 8752 |
| | 872 |
| | 84 |
You follow suit with the 2 (discouraging) and declarer wins the A. Declarer now leads a club to dummy's K. You should play high-low in clubs to indicate an even number of clubs. This is not an attitude situation because of dummy's obvious club strength. If partner has the A, it's important to help him determine when to take it.
The full deal:
| | Dummy | | |
| 85 | |
| J43 | |
| Partner | 963 | You |
| QT4 | KQJT9 | AJ92 |
| QT6 | | 8752 |
| QJT5 | Declarer | 872 |
| A76 | K763 | 84 |
| AK9 | |
| AK4 | |
| 532 | |
When declarer leads to dummy's K, you play the 8. When declarer continues with dummy's Q, you complete your signal by playing the 4. Partner knows that you must have started with a club doubleton, so he holds up his A for a second time. Declarer only gets two club tricks, and is fated to go down.
If instead partner won his A at trick two, declarer could later lead his third club to dummy and collect four club tricks in total. The high-low signal in clubs makes all the difference.
Example: Following Partner's Lead at No-Trumps
Count signals should also be used by third hand when the following conditions are present:
- Partner makes an opening lead against a no-trump contract
- Dummy covers partner's lead with a higher card
- Third hand does not have a higher card than dummy
Against South's no-trumps contract, partner leads the 7:
| | Dummy | | |
| AK876 | |
| Q43 | |
| 93 | You |
| A32 | JT9 |
| | J652 |
| | 8762 |
| | 64 |
When declarer plays dummy's Q you should follow suit with the 6. This can't be an encouraging attitude signal since you'd cover the Q with an honor if you had one. Partner should read you for an even number of hearts.
