This is a tricky haiku constraint because CANAL is concrete, but flexible in a way that can scatter a poem. It can point toward city, waterway, body, dentistry, transport, escape, or metaphor, so the challenge is choosing one field and staying there. auntie jj’s “FRAME the GABBY cook / WACKO used HATCH in CAUSA / lodged in root CANAL” is a strong example of solving that well: the hard prompt words are absorbed into one specific culinary-to-dental chain, so CANAL arrives as the logical endpoint of the scene rather than a visible answer word. Across the set, the stronger entries keep the constraint alive by giving it a precise function — street, bank, drift, drought, root canal, reflective landscape — instead of asking the noun to carry the whole poem on its own.