climbing in and out of the cot

We have 2 cots, a fabric portable cot that we use very sparingly; and a solid wooden cot that we use almost everyday. Before we realised it, he was in the cot! Andrew thought I put him in the cot but I didn't, somehow he managed to climb in. This happened a few days ago... we put him in the same bedroom as ours just for the night because he wasn't well, and we had to use the portable cot in our bedroom because the wooden cot wouldnt fit through a standard doorway unless dismantled. The next morning we found him jumping up and down on our mattress messing around - he could climb in and out of the portable cot freely and easily. So we put the portable cot away and let him sleep in the wooden cot in his own bedroom again. It is obvious that he has grown out of the portable cot, now he is climbing in and out of the wooden cot.... what do we do ?! Not that we mind his climbing up and down but the potential danger of fall that may result from climbing. Our wooden cot has passed Australian Safety standard, the side rails are higher than the lowest point of my rib cage. There are still a lot of clutter we dont want him to touch in his bedroom (and elsewhere in the house!). We have fenced off the living area but he has been attempting to climb over the "fence" trying to go over the pen area ... Arghhhhhhhhhhhhh !!!