I did not know what a heeldo was until this day
if I'm disappointing I didn't know before or horrified that I know now.
A heeldo is a harness for your heel so you can attach a dildo to it.
You gotta be flexible to self fuck as it suggests
Would be cool for foot fetishes and I suppose more comfortable than trying to put it on your toes.
Unless its like a platform boot or something... but that gets into some other kinks.