AusBonsai

What bonsai collars used for

I have no idea what you are talking about In what context did you hear it ?

I've only ever heard it used as part of the bonsai, eg "The collar of a branch".

Do you hook them to a leash when you take your bonsai for a walk?

Probably Webos, I'll buy you one if you like?

hey mate

is this what you mean?

this info is what and arborist would use

Making Proper Pruning Cuts
Pruning cuts should be made just outside the branch collar. The branch collar contains trunk or parent branch tissue and should not be damaged or removed. If the trunk collar has grown out on a dead limb to be removed, make the cut just beyond the collar. Do not cut the collar an arborist would use this method because if you cut past the collar it slows down healing speed
but i wouldn't have thought this applies to bonsai

A collar can be used if you are doing a layer and you need to build up the soil to the layer. it can also be used for root over rock to fill up to the trunkline if you want to bury the roots a little longer. That is what i use them for. I make the collar out of a pot, cut it in half, and then tie it in place to put the dirt in. I call it a collar as i dont know what else i would call it.