Don't guess the balance point, or use fingertips to measure it when you can use a simple, accurate tool like this! If a model is to fly satisfactorily its longitudinal dihedral must be correct, and its flying surfaces warp-free. The final factor is that its CG must also be right. Guessing the balance point, e.g. using your fingertips, can lead to innumerable unnecessary test-flights or - in the worst case - to an immediate crash.
The plan or building instructions usually state the CG position, but how should it be transferred accurately to the model? This problem is solved neatly with this CG Gauge, which is designed to cope with models with an all-up weight of 300 g to 10 kg. The measurement range extends from 30 to 150 mm, which means that it can handle a (non-swept) wing with a chord of up to about 450 mm in the case of a constant-chord wing.