Crib Scaling

It's nap time. It's been nap time for just short of an hour. So you can imagine my surprise when less than forty minutes into nap time I heard a small cry from Sam followed by a thunk.
The cry from Sam did not surprise me. His little body has been working on pushing his one year molars through for a few days now. What surprised me was the thunk. My immediate thoughts were that he dropped his baby doll from his crib, then it occurred to me that it was Ben.
For several months now I have had the boys nap in separate rooms even though they share a bedroom. I like that I can put them down for rests separately and I like that they are less likely to wake each other up prematurely. It works for all of us.
Lately when Ben wakes up he has been scaling the side of Sam's crib and teaching Sam to hold on to the side rail and jump. This happened twice in three days, once following a nap and once first thing in the morning. Brian and I were concerned, and slightly impressed that Ben was able to climb in from outside the crib. Neither of us had witnessed it and Ben's description of how he did it was pretty incomplete.
But today I caught Ben in the act. Usually when Sam fusses I let it go for a minute to make sure he's really awake. If it lasts or picks up in volume I will go and hold him for a couple of minutes and then put him back down. Today Sam's cry was far from an awake cry, thus my concern upon hearing the thunk. I quickly went upstairs to see the door open in the master bedroom. I also saw the door to the boys' room cracked and I know that I always close the bedroom doors when the boys are sleeping. The thunk was one of the door knobs being turned by an eager big brother. I didn't even bother checking the master but immediately went into the boys' room just in time to see Ben standing on the edge of the crib mattress with his upper body hanging over the top crib rail. The weight from his head and shoulders pulled him right over and into the crib. I also saw little Sam curled up in a ball on his tummy not yet fully awake.
Apparently I can be pretty scary. All I said was, "No!" and I had them both in tears. I tried to quickly explain to Ben that he cannot get into the crib with Sam, that it's not safe, while also ushering him back to my bed. I then had to turn my attention to Sam who was now awake and really confused about the entire situation.
It took less than ten minutes to remedy the situation. Sam went back to sleep easily and by the time I went into the master bedroom to check on Ben, his eyes were also closed. Now I wonder if I should start putting the baby gate across the doorway to the boys' room to slow down the process. I've also considered Sam to be the more daring of the two boys which really makes me worry about crib escapes. Yikes!
Ben has taught me several things in the last few days:
*He will get out of bed even if I tell him not to.
*He is now a climber.
*He may have a future in gymnastics....it was a pretty impressive front flip.
*He can now effectively manage door knobs.
*He can't stand to hear his brother cry.
So this is what a three year-old does.....