picked up a bogen today and can't figure out what all the tabs do. are manuals available online or can they be ordered? thanks.

Not that I've ever seen on their site (http://db.manfrotto.com/), but you can prowl around there for yourself.

Why were no instructions provided with the product you purchased, Edwin?

A Bogen what? You'll have to be more specific. Bogen is a distribution and marketing arm of Manfrotto. They put their own name on a lot of products.
try the bogen site
http://www.bogenphoto.com/product

try the manfrotto site, they have some cross references.
http://www.manfrotto.com

A small, fold out manual should have come with it. You should be able to figure everything out. Just play around with it, and don't force anything.

I didn't get any manuals or anything with mine either. Those tabs you are referring to, are to allow the legs to spread out further.

http://www.manfrotto.com/home/literature/index.html

You may have to look up the Manfrotto numbers, there is a Bogen/Manfrotto cross reference.

Edwin,

If you face the 501 head with your hand on the pan handle, (as if you were looking in to the camera's view finder), the controls operate this way:

On the left side of the head is a relatively large knob, as they are called. This locks the head vertically.

Just above this knob, is a small red lever. Push this in when you insert the plate with the camera on it. It keeps the plate from falling out of the head.

In the back of the head is a small knob, just below the plate, at the base of the head. This is your horizontal lock.

Just above this knob, under the plate. is a wheel like object, which is used to place horizontal tension on the head.

On the right side of your head, is a small knob, next to the plate. This locks the plate in place.

Just below that knob, is a large knob, which is your vertical tension control.

Needless to say, unlock your vertical and horizontal locks, before you pan or tilt.

I hope this helps. Good luck with your new TP.