An adobe is made by combining a Reed Bundle (or a straw) with clay. It can be used to build an oven, kiln and walls. It can also seal up a firing kiln to turn the burning kindling inside into charcoal.
As reed bundles can't be stored in a basket or backpack, it's recommended to combine the ingredients at the tule reeds in order to avoid multiple trips. It is also possible to get one extra adobe by using a shovel on tule stumps, or by adding water to various adobe constructions (Adobe Oven Base, Partial Adobe Wall, Adobe Rubble).