A sneck is that horizontal piece of metal on old door catches which rests in the latch. You snap open the sneck by pressing down on the clack with your thumb. It makes noise. A sneck is only 'lifted' if someone is sneaking in, or out. Sounds like a burglar to me. Or a 'dirty stopout' maybe.
As well as a door-latch, 'sneck lifter' is also a type of real ale made by the Jennings brewery of Cockermouth in Cumbria. And apparently it refers to the sixpence with which you could 'lift the latch' of the pub door and buy a pint. Or so it says here: http://www.pub-explorer.com/realale/jenningsbeers. htm
Here in Geordieland sneck is a slang word for nose, as well as the part of a lock that holds the bolt in or out. Having sampled the Jennings Snecklifter brew at a pub in Pooley Bridge, I can confirm that the odour is powerful ( to say the least ) and certainly lifts the sneck!