Why can't I bevel?

This is a question I had to ask myself too many times and every time it makes me feel dumb.

So I’m messing around in blender, minding my own business and then suddenly I find myself trying to bevel an edge, and it just won’t work.

I clean up floating vertices, make sure all edges are connected properly but still find that the bevel seems to have a mind of its own.

It takes me entirely too long to figure out what is going on every single time. So this time I decided to write about it in the hopes of cementing it in my brain once and for all:

Interior faces are the problem

When the edge is connected to an interior face the bevel doesn’t behave as expected. It tries to bevel the interior face’s edge, which is not going to work.

Blender fix: can’t bevel edge

First off you need to select interior faces.

Using xray mode you can see that you’ve indeed selected one or more interior faces.

Now just go ahead and delete those faces.

And try to bevel again.

Note: don’t forget to resharpen the edges

Woo! Note to future self: stop forgetting about interior faces you big dummy.