Do all rods and knobs have a standard threading? We've lost a knob.
There is no standard, and threads may not even be US standard.
Thanks for the warning, brickeye. I'll take the rod to the plumbing store; hopefully I can find parts that will match up.
By any chance are you talking about the rod that controls the pop-up drain? If so, it's fairly simple to replace the rod/knob combo from another kit (you'd have to buy another pop-up drain, or just "borrow" it from a used kit). The rods come in different thicknesses, so just be aware of that and try to find the same thickness rod (it's not essential, but avoids a very loose rod and makes it easier to attach to the arm that operates the drain without it sliding off.
Thanks, Homebound. I am talking about the rod that controls the pop-up drain. The kids have lost the knob off the top; it must have come unscrewed. I may have to buy a rod and knob set. I'll look on Kijiji for a set before looking to buy new. Thanks!