External door locks

[Kos]

I've got one of those wooden door locks where you push the handle up until it clicks and then lock it. Over the past few months the clicking has become more and more difficult to achieve to such an extent that I can't lock the door from the inside. Are there any DIY tips to correct this?

[molly]

I can't claim to be a DIY expert, but perhaps a little WD 40 might help.

[KARL]

Although I have seen these, I have never investigated how they operate but, I think there may be bars which on locking somehow operate rather like vertical bolts between door and frame. If lubrication does not help immediately then investigate whether there are signs that the system is snagging somewhere, either through a hole having gathered debris or the door has started warping (signs of drag causing shiny areas on metal surfaces - concentrate lubrication there).