Set edge as axis for surface rotation Before making a dodecahedron animation I want to construct the lower half as a static object. In my screenshot you see the initial, flat construction, for which I've rotated five pentagons around the vertices of the central pentagon in order to have their edges aligned to each other. The next step would be to set those edges as each pentagon's individual axises and "fold" the pentagons, compared to folding a paper, upwards, so the neighbor edges would align, too, at a certain angle.


How do I set edges as axis for object rotation?
How do I define the meeting points of two edges?


The pivot point of selected pentagon on inner edge, the modifier's local axis is not aligned with the edge.
To rotate the faces around a specific edge, change to Edge Selection Mode, select all the edges of the face you want to rotate and select the edge that the face will be rotating around as last. 

Set Pivot Point as Active Element and change Transform Orientation to Normal. 

To rotate the face around that edge hit R button, then Y button twice, then type rotational angle and hit Enter.

For dodecahedron faces to meet the rotational angle should be around 63.5 degrees (arccos(1/√5)) from the grid floor. 

To use the function for precise rotation, after hitting R button type:

*180*acos(1/sqrt(5))/pi


To change the angle to negative or positive use Ctrl+- buttons