A STUNNING maiden home Test century from Matthew Wade has handed Australia a crucial first-innings lead over Sri Lanka that its batsmen were unable to deliver.

Wade profited from some defiant lower-order support from Peter Siddle (38) and Jackson Bird (6 not out) to reach his milestone just after midday in the series-ending Test at the SCG. Sri Lanka's ploy of packing the off-side with five outfielders proved futile as the Victorian left-hander picked gaps twice in the 107th over to, somehow, reach the rope.

Australia's stronger-than-expected position allowed captain Michael Clarke to declare just after midday and give his team 20 minutes at the Sri Lankan batsmen before lunch. The declaration came at 9-432, a lead of 138 over Sri Lanka, with Wade 102 not out.

Sri Lanka was unscathed in the four-over spell it had to face before the break, reducing its deficit to 122 in the process. It will resume after lunch at 0-18, with Dimuth Karunaratne on 17 and Tillakaratne Dilshan yet to score.

Wade shared a 77-run partnership with Peter Siddle at the start of day but seemed little chance to score a century when the seamer was followed promptly by Mitch Starc (2) and Nathan Lyon (4). Despite only being 70 at the fall of the ninth wicket Wade's chance of tack of hit more lustily paid off spectacularly, although it was also thanks to the diligence of Bird.

While Wade is still to prove entirely convincing at international level with his glovework his reputation as a batsman continues to grow. He thrived on the promotion to number six, as he did on day two, and reached his third Test half-century in the second over of day three before going on to convert that into his second Test century.

The efforts of Siddle, and to a lesser extent Mitch Johnson (13) and Bird, highlighted the benefit of tailenders showing some grit. When Sri Lanka's first bowler came to the crease its innings was over within 15 overs. Despite Australia boasting an even longer tail, with five specialist bowlers, its innings lasted for an additional 36.2 overs once the first tailender, Johnson, arrived at the crease.