You can create a playpen in many ways. If you're not a DIYer, you can purchase play yard fencing. You can also turn a whole room into a playpen by childproofing it thoroughly. An outdoor play area can be created using fencing and a soft ground cover, and you can even construct a playpen out of plastic or wood.
If you want to create a basic play enclosure, playpen fencing is available that's made of plastic, metal or wood. Some playpen fencing is a fixed size or can only be extended a certain amount: the Summer Infant Secure Surround Play Safe Play Yard creates an area of 18-1/2 square feet and has an extension kit that increases the space to 34.4 square feet. Modular playpen fencing is also available, such as Playzone by Friendly Toys, that allows you to add as many panels as you like.
Another option is to childproof an entire room and put a baby gate up in the doorway, creating a giant playpen. Your baby's nursery is a great place to do just that. Make sure any heavy or tall pieces of furniture, like shelves, are secured to the wall with anchors and brackets. Put outlet covers on open electrical sockets, and put power strips inside childproof covers. Tape plugs into outlets if they're being used. Put soft bumpers on sharp edges of furniture. Install safety latches on drawers and cabinets you don't want your baby getting into. If you don't want to or can't put up a baby gate, use a childproof doorknob guard to stop your baby from opening the door.
You can also create an outdoor playpen. Some friends with a toddler recently turned their back yard into a playpen. They lined the ground with Astro Turf, put up wire mesh fencing attached to stakes in the ground, installed a baby gate in the fence for easy in-and-out access, and wrapped a tree trunk in bubble wrap so their daughter wouldn't bump her head on it.
To build a playpen from the ground up, you'll need several square panels of plywood, roughly 3 feet by 3 feet. Make sure the edges are sanded so they aren't rough or splintery. Attach the panels to each other with hinges using wood screws until you have several in a row. Attach a baby gate to the two ends to complete the enclosure.
Choose play fencing that doesn't have sharp edges so the baby doesn't hurt himself. Choose sturdy fencing or playpen panels because a baby could get a limb caught in fencing that has large gaps. If the fencing is too flimsy, it could fall, bend or wrap around the baby.