Section 31(1)(b) in The Punjab Slum Areas (Improvement and Clearance) Act, 1961
(b)if such person cannot be found, by affixing the notice, order or direction on some conspicuous part of his last known place of abode or business, or by giving or tendering the notice, order or direction to some adult male member or servant of his family or by causing it to be affixed on some conspicuous part of the building or land, if any, to which it relates.