What the two letters actually stand for
C&C is shorthand for cubes and Coroplast. The cubes are the wire grid panels sold as flat-pack storage shelving, each a square of welded wire roughly thirty-five centimetres across; clipped together with the plastic connectors in the pack, they form the walls of the cage. Coroplast is a brand name that has stuck to corrugated plastic sheet — the fluted, twin-walled material of estate-agent signs — which you score, fold and tape into a shallow waterproof tray that forms the cage floor and keeps bedding and droppings off your room's floor.
The design took over guinea pig keeping for a simple reason: it solves the pet-shop cage problem. Commercial cages are nearly all too small for an animal that runs laps, while a C&C build gives a pair of pigs a clear running rectangle for less money than the undersized cage, and it unclips and rebuilds bigger the day you have more floor to give.
Size the footprint before you buy anything
Guinea pigs are ground animals, so plan in footprint, not height. A two-grid by three-grid rectangle is the accepted minimum for two pigs, and two by four is noticeably better — the extra grid length is the difference between a pen pigs wander in and a track they can genuinely run. Sows usually thrive at the smaller end; bonded boar pairs argue less in a two by four. A loft or second level counts only as a bonus, never as part of the footprint.
Decide where the cage will live before ordering, and check the rectangle fits with the tray's walls and your access for cleaning. A stand made from a second set of grids lifts the cage to working height and creates storage cubes underneath for hay and fleece — worth building in from the start rather than retrofitting under a populated cage.
Building it, in the order that works
Connect the grid walls first, using the pack connectors at every corner, then run cable ties alongside each connector. The connectors alone can pop under a determined lean or a child's weight on the rim; ties make the frame rigid. If the cage will sit on a stand or have a lid because of a household cat or dog, build that structure now too.
Measure the inside of the frame and cut your plastic sheet larger by the height of the tray walls on every side — walls of around fifteen centimetres suit most pigs. Score along the fold lines with a craft knife and ruler, cutting through only the top skin of the corrugation so the sheet bends cleanly instead of splitting, fold the sides up, and tape the corners on the outside with strong packing or duct tape. Set the tray into the frame, add fleece liners or your chosen bedding, then the houses, hay rack and bottles, and the build is done — most first-timers finish inside an afternoon.
The safety checks that matter
One check outranks all others: count the holes in your grids. Safe grids have nine squares across; older and cheaper sets with five larger squares have holes big enough for a young guinea pig's head to enter and jam, and those panels belong in the shelving system, not the cage. Until baby pigs are around six months old and fully grown out of the risk, line the inside of any grid wall with extra plastic sheet to a good height, because youngsters can also slip whole-body through standard spacing.
Check the tray walls against your pigs' habits too — a pig who stands at the wall and chews the tray edge needs the fleece folded over the rim or a chew strip added, though most lose interest once hay is plentiful. Record the finished measurements, grid count and layout on your guinea pigs' KinsLe profile through Family Sharing, and the day a family member offers to extend the cage while you are away, they are building to the same plan instead of improvising a smaller one.