I recently picked up the book Mountaineering: The Freedom of the Hills. (Great resource.) I'll try to explain the rappelling technique it describes to the best of my ability and then ask a couple questions.
The text shows the anchor set up with web slings and/or static rope, using two opposite and opposed carabiners as the main clip-in point for the climbing rope. This part I understand, but the example provided uses the rope from the middle, so the rope is folded over in half, and then you attach your rappel device to both strands of rope.
Is it acceptable or safe to rappel with the climbing rope tied to the two carabiners with a figure eight knot, and then using only one side of an ATC to rappel down a face? I understand the half rope technique is used to retrieve your rope when you're done, but what about for shorter rappels where I can scramble back to the top of the face?

how ya gonna get ur rope back? is it a walk off (i'm thinkin). if a walk off, is the anchor within reach? is the anchor permenant? if so and you can get to ur rope after the rap and ur doing this because the climb is 150-160 feet then get 170 feet of 6 mill for the other half of the full lenght rap. caution with this as the 6 mil moves faster then ur climbing rope so it should be 10 feet longer. tie a double fish to connect ropes together with the climbing rope through the biners and the dlb fish down rock a couple feet. make sence? always tie knots in the ends and a prussic or other friction knot as a back up.

I recently picked up the book Mountaineering: The Freedom of the Hills. (Great resource.) I'll try to explain the rappelling technique it describes to the best of my ability and then ask a couple questions.
The text shows the anchor set up with web slings and/or static rope, using two opposite and opposed carabiners as the main clip-in point for the climbing rope. This part I understand, but the example provided uses the rope from the middle, so the rope is folded over in half, and then you attach your rappel device to both strands of rope.
Is it acceptable or safe to rappel with the climbing rope tied to the two carabiners with a figure eight knot, and then using only one side of an ATC to rappel down a face? I understand the half rope technique is used to retrieve your rope when you're done, but what about for shorter rappels where I can scramble back to the top of the face?

Also make sure you have knots in the ends of your ropes.

+1

Saved me from a 10 foot ground fall a few weeks ago.

I frequently do something similar in a top-rope situation. The top can be accessible, but via a longish walk. Or, it can be used in a teaching situation for an instructor to get back to the bottom.

As was inferred above, you will have less friction in the set-up than if you are getting friction from two strands of rope. But it's certainly manageable & fine.

I was just curious if that was the only way to do it. Thanks for the info.

If you are setting up a toprope by accessing the top anchors by walking, and you want to rap down to save time, wouldn't you just run the rope through your anchor setup to the middle of the rope and rap off both like a conventional setup? I've done this numerous times. I can't for the life of me think of one where it would make more sense to tie into the anchor with the end of your rope and rap down. Wouldn't you then have to walk back up and set up your toprope again?

One scenario is where the master point of the anchors for the climbing rope is over the edge - well down from the top, but it isn't pleasant to walk down to them; or where the cliff is more than half a rope-length long & the master point extended down so a half rope can be used to TR it.

Hope I've explained that well enough.

If you are setting up a toprope by accessing the top anchors by walking, and you want to rap down to save time, wouldn't you just run the rope through your anchor setup to the middle of the rope and rap off both like a conventional setup? I've done this numerous times. I can't for the life of me think of one where it would make more sense to tie into the anchor with the end of your rope and rap down. Wouldn't you then have to walk back up and set up your toprope again?

I tied up an auto-stop on 7mm line using a double fisherman's knot and a prusik, clipped into the leg of my harness. (I will definitely be tying knots in the ends of my rope.)

Saved my ass a couple of years ago. I was comming of a new to me 3 pitch in the dark in the rain and zipped past the anchers on the way down. My hand hit the knots that were tied in 2 meters above the ends. If those knots were nto there I may not be here.