Thanks to Chris Kelley , the below site shows you what a similar saw looks
like.
HOWEVER, this one is quite expensive and the ones I am talking about from
Home Depot, Lowes (In the USA) are $90-$125 US
http://www.dynabrade.com/cgi-bin/Industrial/12205?QIdhsvtL;;33
If you are cutting into foam, it is not a problem at all. Cutting into
plaster is also easy but you want to cut it at an angle-the blade will go
into the plaster. If you are using preformed “bells” of copoly or clear
plastic, you can take the plastic bell, after it has been pulled over a
model, and put the edge in a vice. Then you just take the saw and cut through
the bottom lip and follow your trim lines.
Mark Benveniste CP