I have been using mudras as a form of healing for many years, and during that time I have noticed that placing the pad of my thumb against the fingernail(s) rather than the tip of the finger(s) feels much more intense, so I became curious.
After researching I have found out that whenever the thumb pad is placed against the fingernail(s) in any mudra, it is the active version of the gesture – it activates the energies of that particular mudra with more intensity than the passive version. The passive version of mudras is for the actual usage of the energy during calm meditation and other less active situations such sitting on public transport.
The Active Gyan Mudra
The active Gyan/Jnana Mudra should be used during powerful breathing practices such as the Agni Sara Pranayama (the Breath of Fire). In my experience, the active version of the Gyan Mudra is even more powerful when the fingernail of the index finger is pressed into the first thumb joint, rather than just placing the thumb pad against the index fingernail.
The Active Pran Mudra
When using the Pran Mudra with both hands, placing the thumb pad against the ring and little fingernails activates the left and right hemispheres of the brain. The hemispheres function equally and in perfect harmony with each other. My experience again has shown me that gently pressing the fingernails of the ring and little finger into the first thumbnail joint makes the active Pran Mudra even more powerful.
Experiment with these variations. I would love to know about your mudra experiences.