Ferret-Proofing A Trundle Bed

Q: I am about to get a new addition to my family, a baby ferret! I am a first-time owner, but have done my research well and I am completely ready for one. But I have a very worrisome problem. I have a trundle bed (a bed with a bed under it). I am very concerned that while playing, my ferret might run under and get trapped in the mess of metal and gears (used to get the bed to a higher position). I am fretting even thinking about the struggle and danger it might be to the poor kit to try and get free, or the danger it might bring trying to free itself or get further in.
 
I was thinking about putting something around the bottom of my bed. Not something entirely permanent (I have friends over that use it sometimes) but something sturdy enough to prevent the ferret from getting into/behind the complex bed. Basically, how do you ferret-proof a trundle bed?
 
A: It is really great that you are planning ahead for your ferret! Probably the easiest way to ferret-proof the trundle bed would be to put some kind of board (like the stuff you can buy for a bathroom wall) or the parts of a pet playpen, using the individual side panels to wrap around the bottom of the bed to create a barrier.

The only problem with ferrets is that almost anything you try to use to ferret-proof will be tested constantly and will often need revisions when you learn where the ferrets eventually get through the blocks. Make sure your ferrets are always supervised while roaming in your room.