T.Q.
15 mos.? My advice is to wait longer. My son started to climb out of his crib when he was under 2. We bought one of those sleep sacs in a large size (you can buy them in fleece or light weight ones). This prevented him from climbing out (couldn't move his legs individually). I even had to put it on backwards for a while when he learned to zip. It worked for a while until he started to throw both legs over the side! At that point I moved him to a mattress on the floor... he was over 2 and it was a difficult transition to get him to nap again, but bedtimes was fine. 15 mos is still a baby and even if he is tall, should still be able to sleep in the crib fine if you can keep him in it! Good Luck!