Why:
Teaching a child to pedal a tricycle can take time, and constantly bending over to offer a push (or restrain the child from taking a tumble) can be murder on your back.  I had some left-over PVC pipe and joints (and short cut-offs, you never can tell when they would be useful) and pieced together this little extension arm that helps both push and control the bike.

Needed items:  
  1 length of 1/2" PVC about 4 or 5 foot long
  3 short PVC pieces (scraps or cut from main pipe)
  3 elbow joints
  1 T joint
  sandpaper and PVC cement

Construction Overview:
The idea here is to make a kind of a C shape at the end of the length of pipe.  The open ends should be at such an angle that they can fit around the tricycle frame when the pipe is held vertically, but are locked when the pipe is down for pushing or holding the trike.

Steps:
* Cut two short pieces of pipe that will join two joints exactly together.
* Attach the T + elbow joint to the end of the pipe and eyeball the length needed to accommodate the tricycle frame (maybe 2-4 inches).
* Dry-fit the pieces together, making sure the twisted-C can both fit over the frame at a vertical but not slip out while horizontal.
* When you are satisfied with the layout, use a marker to mark the angles at which the joints are set
* Disassemble and sand the connection points. 
* Use the PVC cement according to the instructions and piece back together (twisting and holding to your angle marks made earlier).

Once dry, you're all set for going up and down the sidewalk with your little one.