When both hands held in Alapadma hasta are crossed at the wrists and placed near the chest we get the Avahitta hand gesture.

Lets take a look at the viniyoga shloka: (uses)
Srungara Natanechiva Leelaa Kandukadharane
Kucharthe Yujyate Soyamavahitthakaraabhidhaha
This gesture is used to show :
1) Love
2) Playing with balls (can be any balls not just rubber, but also [...]

When both hands held in sarpashirsha hasta is crossed at the wrists, we get the Nagabandha hand gesture.

lets take a look at the viniyoga shloka: (uses)
Etasya viniyogastu nagabandhe he samataha
This gesture is used to show how the snakes twine or their nature of coiling and encircling

When hands in Kapitta hasta is held crossed at the wrists we get the Bhairunda hasta. Some times this hasta is done without crossing the wrists also. Hands in kapitta just join at the wrists.

Lets take a look at the viniyoga shloka (uses)
bhairunde pakshidampatyor bhaiundo uchyate karah.
In Sanskrit the word Bherunda or bhairunda means terrible. [...]

When both the hands in Ardhachandra hasta are placed over one another and only the Thumbs are interlocked we get the Garuda hasta.

Lets take a look at the viniyoga shloka
Garudarthe Viniyujyate
Its says that this hasta is used to denote a Hawk.
It can also denote birds flying.

When both hands in Mrigashirsha hasta and the left palm is placed over the right palm, we get the Varaha hasta.

Lets take a look at the viniyoga shloka of this gesture.
Etasya Viniyogaha Syadvarahartha pradarshane
It means that this hasta is used to denote a Boar or a wild pig. The Varaha avatara of lord Vishnu is [...]

While the hands are in chakra hasta, bend all the fingers (except the thumb and the little fingers) and hold the palms tight.

Lets take a look at the viniyoga shloka
Kurmarthe viniyujyate
The shloka says that this hasta is used to denote a Tortoise. The Kurma Avatar of Lord Vishnu is also denoted by this Hasta.

When the right palm is placed over the back of left palm, both palm being in Ardhachandra hasta.

Lets take a look at the viniyoga shloka
etasya viniyogastu sammatau matsyadarshane
It says that this gesture is used to denote a Fish. The Matsya Avatara of Lord Vishnu is also denoted by this gesture.

When the fingers in Chakra hasta are bent in such a way that there is a hollow at the center of the palm we get the Samputa Hasta.

lets take a look at the viniyoga shloka of Samputa
Varvacgade sampute cha samputah krah iritaha
It says that Samputa is used to denote
1. Concealment of objects. It can be [...]

When the Palms in Ardhachandra mudra touch each other vertically and horizontally we get the Chakra Mudra. The right palm is vertically held and the left palm is horizontally placed over the it.

Lets tale a look at the viniyoga shloka (uses)
chakrarthe viniyujyaate
It says that this Mudra denotes a Wheel. In Sanskrit Chakra means a circle [...]

Hold Ardhacandra in the left hand, palm facing up. Hold shikhara in the right hand and place it on the left hand.

Lets take a look at the Viniyoga Shloka (uses)
viniyogastu tasyeva shivalingastya darshane
The shloka say that this Mudra indicates a Linga of lord Shiva. Linga means sign, mark or symbol. Thus [...]