You must have Battlefield 2 with Update 1.50 installed in order to play Sandbox.
Sandbox Patch - 1.0 » 1.0.1
September 4, 2009
38MB, md5: f5de5cdba8c58ae9ed595d73e6f1e15b
You must have Sandbox 1.0 and BF2 Update 1.50 installed.
ModDB (USA)
FilePlanet (USA)
Sandbox 1.0.1
290MB, md5: b36583067920e15c12bcead1f248a838
Remember to uninstall any older versions of Sandbox first.
ModDB (USA)
FilePlanet (USA)