hi Enrique,
as Dave mentioned, it's safe to use a blade to carefully cut the byssal threads in order to relocate the clam. cut as close to the rock as possible, and go slowly.
i've also CAREFULLY rocked clams over a period of time, which loosens the threads, but this is VERY tricky to do, and you run the risk of damaging the byssal gland if you get impatient, so use a blade if you can. sometimes it's necessary to use a combination of rocking and cutting to get the clam loose. just remember, if you damage the byssal organ, you'll most likely lose the clam.
after you give the clam the once over, if you get a small piece of
LR or a clam halfshell, let the clam attach to that, and if you ever have to move it again, all you do is move the halfshell or
LR it's attached to.
HTH
