"Tayyammum" or "Dry Ablution" can be done in place of Wudu or Ghusal.

Conditions for Tayyammum 

Tayyammum can only be made under the following conditions:

1. If there is no water after making a search for water within a two and a half kilometre (2.5 km) area.
2. If a person is very sick and fears that the use of water will cause more illness or harm to the person.
3. If a person is becoming late for Janazah Salaah or Eid Salaah.
4. If a person fears being attacked by snakes or animals if he or she goes for water.
5. When water is very scarce and only sufficient for drinking purposes. 

How to Make Tayyammum

STEP 1: Make the Niyyah (Intention) for Tayyammum:
STEP 2: Strike both hands on the earth, sand or dust or any object having dust on it. Then, dust the hands clean or blow the extra dust off the hands and wipe the entire face (as done in Wudu) without leaving out any part of the face. 
STEP 3: Strike both hands again on the ground, dust clean and wipe the right arm up to the elbow with the left hand and left arm with the right hand. Make Khilal of the fingers. If one is wearing a ring or bangle, it is necessary to remove it or shift it. If one has a beard, it is Sunnah to also make Khilal of the beard (run fingers through the beard). 

The Fard (Faraa'id) of Tayyammum 

The Faraa'id of Tayyammum are:

1. To make the Niyyah (intention) for Tayyammum.
2. Striking both palms on the earth or dust and wiping them over the face.
3. Striking both palms on the earth or dust and wiping them over the arms till the elbows. 

The Sunnahs of Tayyammum 

The Sunnahs of Tayyammum are:

1. To begin with the "Bismillah."
2. To start with the right hand.
3. To make Khilal of the beard.
4. To make Khilal of the fingers.
5. To make Tayyammum in the proper sequence. 

Objects on which Tayyammum can be Performed 

1. Earth (clean soil)
2. Sand
3. Stone
4. Lime
5. Baked earthen pots which are unglazed.
6. Walls of mud, stone or brick.
7. Clay
8. Things that do not melt or burn to ashes. 

Objects on which Tayyammum cannot be Performed 

1. Wood
2. Metals
3. Glass
4. Food
5. Items which burns to ash or which rots and melts. 

Actions which break Tayyammum 

1. The same actions which break the Wudu or Ghusal.
2. The finding of water.
3. After one is fit.
4. If there is no more danger from snakes or animals.