There are two similes in this poem, and both of them are, well, odd.
Let's take a look at the first:
A Window opens like a Pod —
Abrupt — mechanically — (7-8)
Are you picturing a pod? What kind? A peapod? How does that open? Not like any window you've ever seen, right? There's something askew in this description. You have to read to the next line to get what Dickinson means. The window acts of its own somehow (without human hands to open it. The house is alive! Or is it dead?).
It's fast and mechanical. Again, that's not like any pod you've ever seen open, that is if you have the patience (and free time) to watch a pod open. Is Dickinson just being surreal? In any case, there's something slightly unsettling in this comparison, don't you think.
Here's another simile:
It's easy as a Sign — (22)
Don't believe Dickinson. It's not as easy as she says it is.
First of all, what's with the floating pronoun "it"? What does she mean by "it"? Given her wacky punctuation, you don't know if this "it" refers to the line before, the line after, or the whole enchilada of the poem. If it any of this were as easy as a sign, then why not just put up a sign and skip the whole poem thing? A sign is easy because it's written simple black and white, where a word says what it means. But that's not what's been going on here. It may be easy for the speaker, who has been watching the house intently for all the indications of this death, but that doesn't make it all easy peasy lemon squeezy for the rest of us trying to decipher this mysterious line.