Usually when the yield curve flattens or steepens, we only look in terms of the 2yr and 10yr notes. However, the yield curve is comprised of more than just two points, and thus traders should look across other durations to see if an opportunity arises.
While flattening has taken place, it hasn't happened everywhere. In fact, an opportunity appeared in the 5-30 year portion of the curve.
In structuring a treasury trade, one can buy the “barbell” by buying a combination of short-term (2-yr) and longer-term Treasuries (20-yr), which have underperformed.
Selling intermediate-term securities (5-yr), which have recently outperformed.