It was only a one shot and it was future Klaine if I remember rightly. Basically whenever Blaine needed Kurt to "take care of him" he would tie one of his ties around a lamp in the hallway so Kurt would see it as he walked in. I don't remember that much of the fic but I do know that Kurt spanks Blaine and a lot of the fic was about that specifically.I remember that Blaine loved the anticipation of it and that was something I remember quite well seeing as it was really described in the fic - I think at one point Kurt sort of would fool Blaine into thinking the next blow was coming for ages and ages. In the end I think Blaine sucks Kurt off and then Kurt fucks him.
Sorry I can't remember much more!