While top of the table Hendon were drawing their fifth game of the season, giving Slough the chance to lead the league for the first time in 10 months, the Rebels were reinforcing the widely held belief among the Wexham Park faithful that their sustained bid for championship honours can only continue if they secure the services of a leading striker to net the many chances that they are creating.
Harrow's joy of picking up an unexpected point was marred, though, by the sending-off of centre-back and goalscorer Richard Evans in the last minute for his second caution in three minutes.
Having been fortunate to escape being dismissed in the first half for kicking Steve Thompson in the stomach, Evans was cautioned in the 87th minute for hacking Tony Dennis to the ground and left eccentric referee Bailey with no choice but to send him off minutes later when he pulled Thompson back as the Rebel bore down on goal.
Despite their lowly position, Harrow set off at a cracking pace and Jimmy Bolton, whom Slough have been linked with in the past, smashed a 25 yard drive against the crossbar after only seven minutes with `keeper Trevor Bunting well beaten.
The Rebels' best chance during a frantic opening 10 minutes came when Thompson released Neal Stanley with a delightfully delicate chipped pass. Slough's leading scorer dithered too long over his final shot and Colin Payne was able to block.
Striker turned defender, Evans, looked ill at ease against the marauding Thompson and he nearly presented the Rebels' favourite with a goal in the 50th minute when his weak pass back to Mackenzie fell short. Rather fortuitously for Harrow, Mackenzie blocked Thompson's shot with his knees.
Slough finally took the lead in the 71st minute when Dodd pounced to win the ball from Eamonn O'Connor and set Stanley up to cross low into the Boro goal area where Thompson defied the flying boots of Evans and Mackenzie to prod in his first goal at Wexham Park for seven months and his first anywhere for ten matches.
The lead lasted only nine minutes, however, and Evans thumped home a header from a Francis Cassidy free-kick to end the Rebels run of 517 minutes without conceding a league goal.
Even after this setback Slough should still have clinched the three points and Dennis and new signing John Watt, late of Watford and Chesham United, both had close range efforts blocked by the excellent' Mackenzie.
Harrow Borough Line up
Mackenzie, Payne, Moses, Cassidy, Bateman, Evans, Emmanuel, Scott, Bolton, O'Connor, Adams. Subs: Jarvis (not used), Dicker (for Adams 15 mins)