Sorry, I was getting 'cam' and 'clam' confused.

I had not heard the expression 'clam' cleat ever before. Mine must be very worn because I don't have to pull back on the sheet to release them , I just pull them sideways out of the slot.
I thought these were v cleats.
http://www.ronstan.com/marine/range.asp?RnID=065
I figured mine were some old obsolete fitting that came with the boat 35 years ago
and probably were the original open groove style and the newer closed v style we're to make use of a stop knot . There ya go

. Gotta remember I'm an old power boatie . Spritzig II is the only yacht I've owned.

Although I see ronstan do still market an fully open groove.
So does anyone use jammers on their 563 and where?
Also it appears I'm in the minority here with no winches
And another question now I'm up on the terminology, why would you use a v cleat or clam cleat as a choice and in what situation ? Would I be better to replace the open
clams with closed v's for jib sheets?