HELP! chickens wont go into hen house at night???

I have four chickens, who are all about three months old or so. Every night, instead of going into their hen house, they sleep in the corner of the run, under the hen house, so I have to crawl under there and grab them and make them walk up the ramp every night! Only one of my chickens who is a rescue will actually walk up the ramp every night by herself. The ramp is very wide and has little pieces of wood glued to it for grip. How do I train them to walk up the ramp by themselfs? Our coop is safe from predators, so Im not worried about leaving them out, Im more worried about them being out early in the morning and getting used to it, and then making noise if I dont let them out early enough. Ps. My other three chickens are all bantams, one silkie, and two polish if that helps/makes a difference.