Let's face it, wooden laminated trivets are not really a good idea, lol. solid would be better but still even if unfinished, depending on the species and water content, etc., if items in the 450 degree range or higher are placed upon them, they will scortch, darken, brown out. not a very pretty sight if used daily or frequently.
With laminated ones, one also has to take into the mix the type of glue being used and it's performance under such conditions.
Sorry ccrow, but as i said, i would advise against it unless you put a heat barrier layer between them and the pot/pan/etc..