Specially tied knots in silk* inserted in a mans anus which is removed at the moments of climax. Properly timed the cord is removed concurrent with the contractions pumping ejaculate thus stimulating the anus and massaging the prostate gland resulting in increased pleasure.
*While the name is derived from knots in silk the practice can also be done with beads or balls on a string, or injection molded balls on plastic stems. Or any variation of such.
The Courtesan tugged each bead of the 7 Knots of Love from my ass at just the right moments causing me to explode with pleasure several times before losing consciousness.