I assume you're speaking of the doorknob on your son's bedroom door,
not a child with a custom opening.
The easiest way to fix something relatively simple (and
non-electrical!) is to examine it carefully and see how it works. You
can also look at (and take apart, if necessary) a similar working
fixture. Many doorknobs have a screw-on aspect to a shaft, and a small
screw that presses against (perpendicular to) the shaft to make the
knob lever the mechanism and not come unscrewed itself. Easier to
demonstrate than describe. Is there a small screw-hole with a missing
Whatever -- give it a shot. Work slowly and lay out parts in order, if
you *do* take something apart. You will be tickled when you figure it
out, and have a boatload of confidence to tackle the next job.
A very good suggestion, and I recommend the Reader's Digest Complete
Do-It-Yourself Manual (red and yellow hard cover). It has clear
illustrations and instructions on how to do almost everything in the
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.