Precisely move and align mesh parts and objects based on geometry and measurements from your scene with Mesh Align Plus. Watch clips on YouTube (or GIFs on the wiki) for instructions!

Project Home Page:

https://github.com/egtwobits/mesh_mesh_align_plus/

Wiki:

https://github.com/egtwobits/mesh_mesh_align_plus/wiki

Mesh Align Plus gives you the power to pick features in your scenes (like lines, or flat surfaces: they're called "Alignment Keys"), and align your objects accordingly. You can also edit parts of your mesh using the same basic workflow.

The features you select define how the alignment behaves. To align flat surfaces, for example, you pick a first flat surface in edit mode, then pick a second flat surface, then select something to apply the alignment to: The first surface will move to meet the second surface.

In that example, the flat surfaces you pick can come from any object, and the thing you're moving is also up to you: move one object, or many selected objects, or a mesh fragment while modeling (each workflow follows the same basic steps). You can optionally do weird stuff, like defining a flat surface with 3 verts on 3 different objects (vert selection order matters too!).

Mesh Align Plus can also capture measurements from your scene for your custom transformations. Find a line/plane intersection point, grab face normals for alignments, and measure angles between lines (a line can be an edge, or just two random verts)...and more. Define an invisible axis, for example, and align your space station to lie along it.

Everything in Mesh Align Plus follows those basic concepts: Pick some features, and choose what to apply it to. If you're doing simple stuff like aligning real faces from different objects to each other, you can use Easy Mode. For super complex alignments, though, Expert Mode gives you extreme power and flexibility for defining your keys, and the target(s) you want to move.

Expert Mode for each tool might seem scary, but it's really just a BUNCH of options that allow you to pick features in weird ways: Define a line that starts in the middle of a bunch of verts, and ends at the intersection point of a line/plane, for instance. Don't ask me why you'd need to do that, you're the expert on your own blend files! :D