M39 — Trade By
Teaching unit M39 of the CALLERLAB (New) Mainstream Suggested Teaching Order, effective
1 September 2026. Prerequisites: Pass Thru,
Trade By
At a glance
| Starting formation | The Trade By formation — two facing couples in the center, two couples facing out on the ends |
| Ending formation | Eight Chain Thru formation |
| Timing | 4 beats |
| Unit | M39 of 50 |
Animation
▶ Play this call — pause, step and scrub it: Watching the animations.
Dance action
"Centers Pass Thru while Outsides, who must be Couples facing out, Partner Trade"
— CALLERLAB, Mainstream Dance Program Definitions, revised 29 March 2026.
What you do
The square is arranged with two couples facing each other in the middle and one couple at each end facing out. Everyone moves at the same time, but the two halves of the square do different jobs.
If you are a Center dancer:
- Pass Thru. Walk forward past the dancer facing you, passing right shoulders, and stop.
If you are an Outside dancer:
- Stay in your couple handhold and Partner Trade — walk forward in a semicircle with your partner, passing right shoulders, and finish on your partner's spot, facing the opposite way.
You finish in an Eight Chain Thru formation: the former Centers are now back-to-back on the outside, and the former Outsides are facing in as couples on the ends. The next call is very often Right and Left Thru or an Eight Chain.
Timing
4 beats — the Centers' Pass Thru and the Outsides' Partner Trade are both four beats, so the whole square finishes together.
Styling
"Same as for Pass Thru (page 44) and Partner Trade (page 63)"
— CALLERLAB, Mainstream Dance Program Definitions, revised 29 March 2026.
In plain words: Centers pass with a natural arm position and the Man's right shoulder slightly forward; Outsides swing their joined hands backward slightly as they release the couple handhold and turn the correct way.
Restrictions
The manual states that the Outsides must be Couples facing out — that is what makes the Trade By formation. It also records that the Ocean Wave Rule applies to the Center dancers, for example from a 3/4 Tag formation, so the Centers may begin in a wave rather than strictly facing each other.
Common faults
| What happens | Why | The fix |
|---|---|---|
| The Centers and Outsides collide | Nobody agreed who is active | Everyone moves, but Centers pass through the middle and Outsides trade on the ends |
| An Outside dancer Turns alone | Forgetting the couple handhold | Outsides do a Partner Trade — you and your partner move as a pair |
| The Centers end facing their partner | Turning after the Pass Thru | Centers do a plain Pass Thru and finish back-to-back |
| The square does not balance | One half moving faster than the other | Both halves are four beats; adjust your speed to finish together |
Where you meet it
Trade By is how you turn the Trade By formation into an Eight Chain Thru formation, ready for a Right and Left Thru or a Square Thru. It is one of the standard ways to bring the square back to an Eight Chain Thru. See the course overview for where this unit sits.
Related calls
- Partner Trade — the Outsides' half of the call. See M32.
- Pass Thru — the Centers' half of the call. See M07.
- Right and Left Thru — the usual next call from an Eight Chain Thru. See M10.
- Right/Left Hand Trade — a two-dancer call with a confusingly similar name. See M32.
Also called / formerly
The call is always called "Trade By". Do not confuse it with "Trade by the Right", which is the two-dancer Right/Left Hand Trade — the manual warns that callers outside English-speaking countries may need to say "Trade with the right hand" instead.
Manual source: Mainstream Dance Program Definitions, revised 29 March 2026, page 63. Reproduced under the permission in sources and attribution.