Their commendable sixth-wicket stand of 139 runs saw the Knights total advance from a paltry 59/5 to a respectable 198/6 and by stumps the visiting Free Staters trailed by 131 runs.
The Cobras signed off their first innings at 330 (111.5 overs) in the morning session to which the Knights replied with 199/6 at the close.
The Knights' first innings was progressing at a fair pace of about four runs to the over, thanks to Reeza Hendricks (26) and Dean Elgar (28), but then Cobras' opening bowler Vernon Philander (4/36) struck with a venomous spell in which he captured four wickets. Philander picked up his wickets in the 15th, 17th and 19th (2) overs.
At the other end, Philander's new-ball partner Rory Kleinveld chipped in with a wicket and during a five-over passage they left the Knights' innings tottering at 59/5.
At that stage, all the Knights would have been concerned about was passing the follow-on mark but Dippenaar and McLaren thought otherwise and defied the Cobras attack for 55 overs.
Two overs ahead of the close, spinner Claude Henderson undid the stubborn partnership when he claimed McLaren's scalp, with the total on 198.
Dippenaar and Obus Pienaar saw the side to the end of play with a further run in the remaining two overs to go to stumps at 199/6 (76 overs).
Earlier, Knights paceman Dillon du Preez put the skids under the Cobras batsmen who were trying to build on their overnight total of 290/5 (93.5 overs).
The 28-year-old seamer ripped through the Cobras batting in spectacular fashion with a five-wicket haul. By the time the Cobras innings had crumbled Du Preeez's figures in the morning session were 8.5-0-10-5. It was his seventh first-class five-wicket haul.
Ryan Canning was the only Cobras batsman to defy Du Preez and he was 30 not out (overnight 0 not out) by the time the innings collapse was complete.
In the day's opening 18.1 overs the Cobras managed a mere 40 runs for the loss of five wickets.
The Cobras picked up 3.92 batting bonus points and the Knights' bowling effort was worth 2.
Scoreboard:
Toss: Cape Cobras
Cape Cobras first innings: (o/n 290/5 -- 93.4 overs)
A Gray c Dippenaar b Pienaar 24
A Puttick lbw McLaren 35
S van Zyl c Dippenaar b McLaren 29
J Ontong c Van Wyk b Pienaar 102
R Levi c Pienaar b Mpitsang 64
J Kemp lbw du Preez 20
R Canning not out 30
V Philander lbw Du Preez 1
R Kleinveldt c Hendricks b Du Preez 1
C Henderson c Dippenaar b Du Preez 0
M Zondeki c Rossouw b Du Preez 0
Extras: (b1, lb12, w1, nb10) 24
Total: (all out) 330 -- 111,5 overs
Fall of wickets: 1-46, 2-80, 3-129, 4-260, 5-288, 6-308, 7-318, 8-326, 9-330, 10-330
Bowling: R McLaren 30-10-65-2 (1w, 1nb), V Mpitsang 21-5-57-1 (5nb), D du Preez 23.5-8-53-5, A Pienaar 15-5-37-2, T Tshabalala 9-0-49-0 (4nb), D Elgar 9-1-36-0, R Bailey 4-0-20-0
Knights first innings:
R Hendricks c Kemp b Philander 26
D Elgar c Gray b Philander 28
R Rossouw lbw Kleinveldt 5
B Dippenaar not out 65
R Bailey c Canning b Philander 0
M van Wyk c Gray b Philander 0
R McLaren c Canning b Henderson 63
A Pienaar not out 0
Extras: (b4, lb6, nb2) 12
Total: (for 6 wickets) 199 -- 76 overs
Fall of wickets: 1-52, 2-57, 3-59, 4-59, 5-59, 6-198
Bowling: Philander 14-4-36-4, Kleinveldt 19-9-53-1 (1nb), Zondeki 15-7-25-0 (1nb), Henderson 23-6-60-1, Ontong 5-1-15-0.