rob the magnet raises the internal bb to unlock the knuckle, but does not open the knuckle. when you pull away with whatever the unlocked coupler knuckle will open but the other coupler knuckle will still be locked. there is no internal spring like thing to open a knuckle that has been unlocked. i have tried the couplers in antisipation of sergent making them for o scale. i did not get sergent's uncoupling tool, but made one up with s 1/8" diam magnet glued to a dowel. i also acc'd a bit of wire which sticks down from the magnet's bottom. this allows you to lift the ball and pull open the closed knuckle with the wire. works great. hope that clears up any confusion. there is a good link on sergent's website that reviews the coupler and has some hints.
