Sequential Bargaining Consider a sequential game with two players who use the following procedure to share two desirable, identical and indivisible objects. Player 1 proposes an allocation in stage 1 which player 2 either accepts or rejects. In the event of rejection, neither player receives either of the objects and in the event of acceptance the objects are allocated according to the proposal of player 1.

The subgame perfect Nash equilibrium of the game is where player 1 allocates both the objects to himself and player 2 receives nothing. Is there any Nash equilibrium of this game other this?
What is the difference for player 2 between accepting nothing or rejecting? None. Therefore, we may say that from the point of view of player 2, he is indifferent between accepting nothing or rejecting. 

What is done, as in Rubinstein's (1982) Bargaining Game, is to assume that in indifference, player 2 accepts receiving nothing, which also has more implications when the game is extended to an extra round where players change positions in case of player 2 rejecting the proposal on the first round, or when is included an outside option. 

EDIT: 

Following the comment from denesp, I will complete my answer. 

The previous reasoning is applied mainly to SPE. If we want to see if there is any other equilibrium, we can start by representing the game in normal form, such that, we can identify two equilibria. 


Player A offers 2, and Player B accepts 
Player A offers 0, and Player B accepts.


However, the last one is not SPE because precisely in Rubinstein's model (and in other bargaining models), it is assumed that if player B is faced with two options that have the same payoff (when involves accepting, and the other rejecting), then he accepts.