However, Boro, who came up with Shields at the end of last season, were held to a 1-1 draw at the Don Amott Stadium by Mickleover Sports.
Steve Kittrick's side would have gone above Shields with a win, but trailed right on the stroke of half-time to a Isai Marselia goal for Sports.
Boro weren't behind for long, however, as James Walshaw popped up with their equaliser just 2 minutes after the restart.
They weren't able to find a winner though and had to be content with share of both the points and top spot.
Relegated Gainsborough Trinity are determined to make a swift return to the Vanarama National League North and moved up to fourth spot after a 1-0 win at the Northolme against the team who came down with them at the end of April, North Ferriby United.
A neat, dinked finish from Damian Reeves right on the stroke of half-time proved enough for Trinity in the end.
It's been a strange start for another newly-promoted side, Basford United.
They were beaten 3-1 at Marston Road by Stafford Rangers to make it five defeats and five wins in the league for the Nottinghamshire side.
They took a 17th minute lead through Liam Hearn, but Rangers were level through Luke Jones within 6 minutes.
Just 2 minutes later, Sam Coulson put the hosts in front and then on the half-time whistle, Kyle Perry made it 3-1.
The evening's other game saw Workington AFC and Marine AFC share a 1-1 Borough Park draw.
Both goals came within 2 minutes of each other midway through the first half, with Sam Joel's opener for the Reds being cancelled out by Danny Mitchley.
By NonLeague Today's Steve Whitney
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