Apparently it feels good to rub yer willy in that cleft... or so I hear from somewhat out of date Japanese sources. Is that still the case... Mz Marmz?
Unsure, since my penis envy is no substitute for an actual cock, so I can't speak with any degree of certainty, but personally, I recon the mystery of the female G Spot is lurking in that fold somewhere.
Funny you should say that cos I haz intense fanny envy and can't really imagine that working as a substitute even with my limited reference. I can confirm that putting one's willy in some things feels better than others and that doesn't necessarily map on to reality in any way, shape nor form one would wish to imagine it doing so.
G-Spots are easy. Second knuckle, come hither come hither, rough patch amongst the smooth, squirty-squirty. Keep up at that back, gal 8)