In Macbeth, Lady Macbeth says, "But screw your courage to the sticking place,/ And we’ll not fail." In your own words, explain what this means.

Lady Macbeth is telling Macbeth that as long as he is not afraid, their plan to kill Duncan will not fail.

When Macbeth tells his wife that three witches prophesized that he would be king, she is excited. However, Duncan does not name Macbeth as his heir. That means that the only way Macbeth will become king is by killing Duncan and getting rid of the king’s two sons. She fears that Macbeth doesn’t have...

Lady Macbeth is telling Macbeth that as long as he is not afraid, their plan to kill Duncan will not fail.

When Macbeth tells his wife that three witches prophesized that he would be king, she is excited. However, Duncan does not name Macbeth as his heir. That means that the only way Macbeth will become king is by killing Duncan and getting rid of the king’s two sons. She fears that Macbeth doesn’t have it in him.

Glamis thou art, and Cawdor; and shalt be
What thou art promised: yet do I fear thy nature;
It is too full o' the milk of human kindness
To catch the nearest way: thou wouldst be great;
Art not without ambition, but without
The illness should attend it … (Act 1, Scene 5)

Lady Macbeth knows her husband. He is not really the type to follow through on such a vicious plan. She points out that while he is ambitious, he will not do what needs to be done.  She doesn’t think he can kill Duncan.

Macbeth does indeed lose his nerve. Lady Macbeth makes a plan to kill Duncan and tells him all he has to do is follow it. When he still worries that they will fail, she tells him to be a man and do it.

What beast was't, then,
That made you break this enterprise to me?
When you durst do it, then you were a man;
And, to be more than what you were, you would
Be so much more the man. (Act 1, Scene 7)

Literally, the “sticking place” refers to a crossbow. A soldier would adjust the cross-bow and arrow to the proper place to make a shot. It is a metaphor for Macbeth adjusting his mindset to the point where he is brave enough to follow through with killing Duncan.

Lady Macbeth is successful in getting her husband to act, and even chides him when he doesn’t leave the knives behind in Duncan’s room to frame the guards they killed.  Malcolm and Donalbain both flee, afraid they are next.  Macbeth becomes king. The plan worked like a charm.

Although Macbeth asks the stars to hide their fire and seems really gung-ho about killing Duncan in the beginning of the play, he appears to be a man whose bark is worse than his bite. He might be ambitious, but he is also careful. His wife, on the other hand, gets things done. She does not care what the consequences of killing Duncan might be. She just wants Macbeth as king.