This is a very dangerous thing to think. Any of us can make a human error mistake anytime. As a result, we should do everything in our power to keep such a mistake from happening. Things to consider include, tying knots at the end of the rope before belaying or rappelling, using an autoblock for a rappel, wearing a helmet, etc. In this blog post, we will go through the steps required for a safe and fun climb.
1) Anchor -- Is the anchor you built for the climb adequate? If you're top-roping, are there two opposite and opposed locking carabiners at the top? Are the pieces good? If you're using bolts, are the bolts good?
Does the belayer need to be tied into a bottom anchor? The default answer is, "yes." If the belayer is not tied into a bottom anchor, you should be able to articulate why.
2) Belayer -- Is the belayer's harness on correctly? Is it doubled-back? Is the belay device threaded properly? Are you using a locking carabiner on the belay device? Is the carabiner locked? Usually a visual check is not good enough to prove that a locker is locked. It's always good to give it a quick squeeze check. Is his helmet on properly? Does he have a nut tool to remove gear if he's going to follow?
3) Climber -- Is the climber's harness on correctly? Is it doubled-back? Is the belay device threaded properly? Is he tied-in properly? Is his figure-eight dressed and neat? If he is leading, does he have the rack? Is his helmet on properly?
4) System -- Is the system closed? In other words, have you made sure that the end of the rope is either tied directly into the belayer or that there is a knot at the end? Open systems are responsible for a large percentage of climbing injuries and fatalities.
5) Commands -- Are you both on the same page as far as commands are concerned? Many people use different variations of commands and it's not a good thing to get them mixed up.
6) Multi-Pitch -- Do you have the climbing topo? Do you have food, water and clothes for the day? What is the weather forecast? Do you have a second rope in case you need to descend in an emergency? Do you have extra cordage and sling material to leave behind? Do you have a strategy?
Climbing is a game with few rules. One of those few is to make sure that you are completely prepared for the situation at hand. Go through the check-list every time. It could save somebody's life...
--Jason D. Martin