Two extra time goals ensured Hartlepool United scraped past non-league Salford City into the FA Cup Third Round.
Pools had struggled to create opportunities against the Evo Stick Northern Premier League side before Fenwick headed home in the first period of extra time.
Sunderland loanee Mikael Mandron volleyed home with seconds remaining to seal the second round replay win.
The result means Hartlepool progress to face Derby County in the next round.
Rakish Bingham had the first shot of the match but his low shot from the edge of the area was saved comfortably by Jay Lynch.
Jake Gray tried his luck from a similar distance five minutes later after beating a Salford defender but his tame shot was saved.
James Poole missed the best chance of the first half in the tenth minute after Trevor Carson spilled a cross from the Salford left.
The former Pools man had the goal at his mercy but fired over from the edge of the six-yard box.
Nicky Featherstone had another effort on goal for Pools after 28 minutes, following good work from Connor Smith and Gray, but the midfielder shot straight at Lynch.
The non-league side again came close to an opener ten minutes before the break when, after good hold up play from Danny Webber, Lewis Hardcastle narrowly fired wide of the left hand post.
Pools had the majority of the possession in the remainder of the half but failed to create a clear opportunity before boos rang around The Vic to greet the half-time whistle.
Half-time: Pools 0-0 Salford City
Salford had the first meaningful effort of the second half when Poole found Webber in the area who then laid the ball to Hardcastle but the youngster’s shot rose over the bar.
Hardcastle almost opened the scoring just after the hour mark when his shot from outside the area was heading for the bottom corner but Carson managed to get a hand to the effort.
The Pools keeper was quickly back on his feet to save from Poole who was following up in the box.
Pools narrowly escaped falling behind later in the half when a corner from Webber was loose in the six-yard box before the referee blew for a foul on Pools’ keeper Carson.
Salford, who continued to dominate proceedings, came within inches of a goal in the 79th minute through a deflected Richie Allen strike.
Adam Jackson fouled Hardcastle to give the seventh-tier side a free-kick in the D, and substitute Allen’s powerful shot deflected just wide of the left-hand post.
The home side’s best opening of the second half came when Carroll burst into the area down the left and fired a low cross across goal but the Pools forwards failed to connect.
Pools failed to create another chance on goal before boos again rang out at the end of the 90 minutes.
After 90 minutes: Pools 0-0 Salford
Pools finally made their breakthrough seven minutes into extra time through Fenwick.
Following their best forward play of the night, Pools played the ball to Rhys Oates wide on the right who crossed superbly for Fenwick to head home after finding space in the six-yard box.
Fenwick could have sealed victory three minutes later after he chased down a long clearance and beat the Salford defence to the ball, but his shot was saved by the legs of Lynch when through on goal.
Pools again came close in the second extra period. Fenwick nutmegged Steven Howson on the right wing and played the ball into the box towards Mikael Mandron but Lynch managed to grasp onto the ball.
In the dying seconds with Salford pushing for an equaliser, Brad Walker crossed for substitute Mandron who volleyed home emphatically.
Pools will now play Derby at Victoria Park on January 8-11
Hartlepool United: Carson, Magnay (Harrison 85), Jackson, Bates, Carroll, Oates, Featherstone, Gray (Walker 66), Smith (Mandron 66), Fenwick, Bingham.
Unused subs: Bartlett, Richards, Woods, Oyenuga,.
Goals: Scott Fenwick, Mikael Mandron
Booked: Magnay, Bates
Salford City: J Lynch, C Lynch, O’Halloran, Stopforth, Howson, Dawson, Hardcastle (Mwasile 105), Burton, Webber (Allen 77), Hulme, Poole (Seddon 82).
Unused subs: Giverin, Clark, Kebbie, Dootson.
Booked: Stopforth, O’Halloran.
Referee: J Simpson
Attendance: 4354 (352 away)