Ridecamp: [RC] Knots

What is the best knot to tie a lead to a rope halter? The leads with the eye splice in the end don't come off easily if the horse pulls back and tightens it. My farrier used a bowline knot, but I have also heard of a sheet bend being used. Isn't a sheet bend the same as the knot you tie the halter on with? I would like it to stay tied until I undo it, and not become impossible to untie if the horse does pull. I don't have any "hard pullers", but have had some freak incidents where pieces of broken hardware have come flying past my head. 

                                                   Shelly