This is a simple but very effective way of keeping a check on all your gear. At the crag, unroll, hang up and check all the gear to make selection easier. This is surely far better than a bagful of spaghetti that has to be sorted! You want to get climbing.....
After your day, some gear may have been 'loaned', so you can immediately see that everything is in place. More importantly, all your gear will be kept clean and free from grit which can jam bearings and screwgates - not good!
Keep all your gear free of tangles, roll up and store in a smaller space in your rucsac.
Summary - Instead of a load of tangled gear at the bottom of a gritty sack, keep all your equipment neat, tidy and clean in a small pack. GEAR-PAK is simple but very effective!