Stupid Question

my shimano spds cannot be removed with a pedal spanner, need an 8mm alan key. get one from isaac lord which will be nice and long for extra torque and cheaper than a bike shop. just remember that now you are turning the tool from the wrong side of the thread so the direction will change.

Sounds like you have the more upmarket Shimano pedals (i.e. not the £15 jobbies that you remove with a spanner).

If I remember correctly I use an 8mm hex bit/allen key to remove mine (I remember this as I made a point of making sure my mini wrench had an 8mm bit), you poke it through the back of the pedal spline (on the opposite side of the crank to the pedal itself, so the side closest to the frame). If you're lucky your multitool may have one on, otherwise you'll need to make a special purchase.

The nut is what you should have been using the spanner on. After removal, there should be a clear hole through the crank.

... unless I've misunderstood what you're trying to do.

Depending on the pedal you can usually remove it with an allen key if you don't have a pedal spanner. Just look through the crank and see if you can see a hex fitting then just use the right size key.
Don't forget right pedal is right hand thread left pedal is left hand thread and if done with allen key can be a little confusing.
The link that rasalati posted shows the allen key method as well.

Assuming you mean what tool to use to remove / secure them, you're after a 15mm pedal spanner / wrench (two words for the same thing, but comparing products you'll probably want to search for both).

You should be able to pick one up from any decent bike store, on or offline.

See also: http://www.condorcycles.com/workshop/how-to-remove-pedals.html.