Canterbury looked in a precarious position after being dismissed on day one for 204, but responded by routing Central Districts for 168.
Half of CD's total was thanks to Will Young's 84, who was the last man dismissed as only three other Central batsmen made double figures.
Canterbury added to their first innings buffer with an excellent beginning to their second dig, with Leo Carter unbeaten on 76 at stumps as Canterbury moved through to 171-3, and a lead of 207.
Elsewhere, Northern Districts have a small lead over Otago thanks to a strong lower-order batting display.
After having dismissed Otago for 237, ND received several key contributions as they reached 324 in response on the University Oval wicket.
Skipper Daniel Flynn picked a good time to find some form, making his highest score since last October with a well-compiled 92, anchoring the top order as wickets fell around him.
Anton Devcich found the boundary often in making 49, but Northern still needed lower-order hitting to snare a sizeable first innings lead; hitting they received from Daryl Mitchell.
Mitchell backed up his century from last week with a composed 73, and combined with Scott Kuggeleijn (32) and Jimmy Baker (28) to give the visitors an 87 run lead.
Otago reached 32-0 at stumps to reduce the deficit, and will need their impressive top order to fire to take control of the contest.