How to block someone on Snapchat
To block someone on Snapchat, open a chat with your (former) friend. Tap the stack of three horizontal lines on the top left corner to open the menu. Now select "Block." The chat will disappear and you'll be freed from the tyranny of their terrible content. If you want to take less drastic measures, you can opt for just removing them from your list of friends by selecting "Remove Friend."
What happens when you block someone on Snapchat
Once you block someone, they'll no longer be able to view your story or snap/chat you. You'll be removed from each other's friends list, and your username will no longer be searchable. If you only "remove" them, they'll still be able to see your public stories, whereas a block will totally prevent them from witnessing any inspired selfies.
How to tell if someone blocked you on Snapchat
You're not going to be directly notified if someone blocks you. You might notice that you're not seeing their stories anymore, are unable to find their username, and that they generally seem to have disappeared from the app. They might still show up in your chat history, but you'll be unable to snap them. But that's not enough to know for sure whether they've unfriended you or blocked you. That comes down to whether you know for sure that they have an active account and you're not able to search their username.
Does blocking someone on Snapchat delete saved messages?
Your chat history with them will disappear on your phone, but it'll still show up on your former-friend's. So they'll still be able to see any saved messages between you. You, however, won't have access to those messages.
If you block someone on Snapchat will they know?
The short answer to this is no, for the reasons we talked about above. It's possible that they'll think you deleted your account, but if they see you snapping a friend of theirs, the jig, as the kids say, will be up.