Transits are often used in archeology, surveying and major construction. But if you are doing something less complex than searching for a lost tomb, you can sometimes get by with a simple homemade transit. For example, if you are trying to level your yard a bit, so you can create a new garden, this basic transit will serve your purpose.
Tape you bubble level to the top of the camera tripod, but don't tape it too close to the center.
Draw a set of crosshairs with a pen over the plastic, then tape the clear plastic over the end of the telescope or scope. Use a ruler and compass for accuracy.
Attach your telescope or scope to the top of the camera mount. If the scope has a thread that fits the mount, you are in luck. However, it is likely that you will need to duct tape it in place.
Use the ruler to mark off the measurements on the pole. They need to be very clear. The best way to do this is to paint alternating black and white horizontal one inch strips. Next to each strip, write in the height in inches. This will be your stadia rod.
Level your transit. To do this, adjust the camera mount knobs until you can turn the mount 360-degrees without the bubble leaving the center of the level. You can now use your transit and the stadia rod you made.