Stacking feet and sockets are the alignment interfaces when cages stack; they determine whether the stack is stable and will not slide sideways. Many buyers only look at the mesh and neglect these two. Empty cages folded and stacked high, and loaded cages multi-layer stacked, all rely on these two parts for alignment.
Stacking feet are welded at the four corners of the base frame, usually as downward-projecting tapered short tubes or stamped steel feet, generally 30~50mm high; their role is to transmit the upper cage's weight precisely to the top of the lower cage's posts, while forming a tapered guide so that even if the forklift lowers off-center, it slides into place automatically.
Sockets are at the four corners of the top frame, made as recessed square holes or flared mouths, sized to match the stacking feet with a clearance of usually 2~5mm. Too little clearance makes alignment hard, and a forklift jolt hits the corner; too much clearance makes the stack wobbly, shifts sideways under full load, and risks tipping above 3 layers.
On-site check: lift an empty cage, align and lower it, and listen for a crisp seating sound; push the side of the upper cage by hand—if all four corners do not wobble, it passes. If a stacking foot is welded off-center, the whole stack leans; on acceptance, set all four feet on a flat plate and check the height difference, which must not exceed 2mm.
Practical advice: when stacking exceeds 3 layers or forklift stacking is frequent, require the manufacturer to thicken stacking feet to 4mm steel plate and add bushings to sockets. The standard cages of Nanjing Tongnuo Warehouse Equipment Manufacturing Co., Ltd. all have guided sockets at four corners, and the taper can be enlarged according to stacking height requirements.