Well, I do have a doorbell though it distinguishes itself by occasionally not working (which is not, I feel, a useful quality in a doorbell), so it's supplemented by a 'please knock! – if no one answers please leave behind the porch or, if signature required, with [housename] next door' sign (complete with a little map showing precisely where the back of the porch is, because what's obvious to me doesn't seem so obvious to couriers, and really it is exactly where you'd think it would be).
Of course, one of the parcels arrived without even a knock. Though it was at least behind the porch rather than just left on the step to entice any thieving scrote who happens to be wandering up the hill (like I say, things obvious to me don't seem so obvious to them).