since most orchids are epiphytic, would it be possible to use some wire or fishing line to attach an orchid to a piece of wood if i were going to keep it in a terrarium where it would stay nice and moist? once i find homes for my hermit crabs, i plan on turning their old 20g fish tank into a terrarium with my cattleya orchid and some other plants, and i was thinking it would be cool to get a piece of wood to go through the center of the tank with the orchids atached to it, with the other plants growing below it.

yes, it is very possible to do this... it is called mounting.... alot of orchids are sold and kept in this fashion....
the tricky part is keeping mounted orchids thriving in a terrarium.... they need humidity, but, 90 percent or better humidity like in most terrariums, usually is not good.... also, they do need a bit of air movement which is hard to get in a terrarium and still keep a balance...
the lighting part can be tough as well.... check out tropiflora or black jungle for plants more suited for a terrarium environment....
thank you