ObWeight
Need an approximate weight? This is not an exact weight (on some devices it is pretty accurate), but in need ...

Place the unit on a soft surface or hold it in your palm. Before starting the measurement, calibrate the scale. Then place what to be weighed on the device, and measure the weight.

Calibrate - Set zero value
Tare - Set weight of container (to be subtracted)
Measure - Measure the weight (or set reference weight)

It may be useful to have a reference weight with you, as a key set. And remember, the accuracy is very poor so you get only an indication of what the weight is. The quality of the measurements is highly dependent on the device used.