Sometimes geometry comes into Maya with difficult tessellation; the original designer might have never intended the model to be edited in the first place, or, more likely, was a lunatic.
Take, for example, this knurled surface by aubenc (not a lunatic, AFAIK) on Thingiverse. All those edges on the top surface N-gon trace to a single vertex. Performing an extrude on that top surface is going to get messy and difficult to deal with down the road.
So, how to delete that collection of edges and replace with a nice clean N-gon?
There’s always the brute force solution, hand-selecting each edge by picking them with the selection tool. This’ll work, but it’s tedious and one always runs the risk of accidentally selecting an edge somewhere else on the model.
Sometimes it’s possible to switch to an orthographic view, drag-select all the edges on a face from the side, and then CTRL-select the edges you dont want from the other side.
This technique will work with a model that’s oriented nicely along the X and Z axes like this knurled cylinder, but what if you can’t get a clean orthographic selection? Like in this (admittedly fabricated for the purposes of this blog post) case? There are no guarantees that a model you find out there in the wild is going to be well-positioned by the time you get to it.
Here’s where Maya’s selection conversion tools become astoundingly useful. First, switch to perspecive view and hit F9. This will put you into component selection mode. Select the single vertex that is common to all the edges you want to delete.
Hold down the CTRL key and then hit F11. This will convert your vertex selection to faces. (CTRL-F10 will convert to edges, by the way.)
Right click and use the contextual menu to switch to face selection.
Hold down CTRL again and unpick the faces that you don’t want in your selection.
Then delete the unwanted faces.
With most models, Polygon-> Fill Hole will give you a nice, clean N-gon if you select a border edge before applying it.
With some fiddling and fuddling and boolean magic, Aubenc’s model became the base for the thumbscrews in Zheng’s GoPro Gubbinses.