Leaflets are meant to go in the bin, thats why we only get a tiny percentage of work from them, but you can generate work from them, just the same as you can from any form of advertising,
If you place an advert in the paper, the only people that will ring you are people who need you, same as leaflets
if you spend £150 on 10,000 leaflets and get only 20 customers at £10 per month,( as an example only as you can build a round on this amount).. that is still £2400 in one year !
So money well spent,
but door knocking is simply a faster way to build a round. because its instant and you are pushing them into finally getting round to getting a window cleaner.