Nearly every climber starts with their climbing career with toproping. This is where beginners learn the art of rock climbing.
One of the most important baseline skills is toprope belaying. Almost universally, most guides are now teaching the PBUS technique to beginners. PBUS is an acronym for the following:
P - Pull
B - Brake or Bottom
US - Up-Slide
In other words, your guide hand is on the line coming out of the device and running up the rock to the climber. Simultaneously, you
PULL down with your guide hand, while you
PULL slack through your device with your break hand.
After you've pulled,
BRAKE the rope with your break hand by bringing that hand down toward your hip.
Once the rope is in BRAKE position, reach down below your break hand and grab the rope. Then you can slide your break hand back up to the device. This is the
UP SLIDE.
Once you've completed these steps you will be able to put your guide hand back on the rope coming up and out of your belay device in order to repeat the whole process again.
When you're ready to lower the climber, always put both hands below the device in order to create redundancy.
The following video by Julie Ellison and Climbing magazine demonstrates the process. And though Julie never uses the PBUS term, this is exactly what she is demonstrating.
There are those out there who still use the old Slip-Slap-Slide technique. If you don't know what that is, you can find a video of it
here. Many people are really freaked out by Slip-Slap-Slide, primarily because it is often done really poorly. Many people who use the technique make significant mistakes and the only reason there haven't been more tragedies with this technique when performed poorly is pure luck.
Guides no longer teach the Slip-Slap-Slide technique to beginners. And indeed, there are some guide services that won't allow their students to use the technique at all. With that in mind, I would never personally condemn someone who uses the technique and does it properly. However, I don't believe that it's an appropriate technique for beginners. The PBUS is the most modern toprope belay technique and should be employed as the primary defense against a climbing fall...
--Jason D. Martin