Hi my tortiose is in a vivarium and keeps pacing up and down. Im worried he is stressed. Its a glass front vivarium. Rather than buy a table could we put wood say a quarter of the way up the front straight across the glass and then slide the glass open. It would still have a roof but air could then circulate through the open glass front and Tommy wouldnt think he can get out of the glass front?

Yes a good idea, have your basking spot at the glass end, the open side will then allow it to cool off. If you provide more details re your tort, - species, age, etc, I can offer a few other bits of advice.
Regards
Tom