Most swiftlet farms would have iron doors for security and there is often a design of a small “door” that enable a farmer to open or close the lock(s) inside the door so as to make it difficult for thieves to cut it. If the owner simply try to open the inside lock without any precaution; he or she might fumble and let the key fall inside the farm. Unless there is a ready spare key, the unfortunate owner will have to go back to his home or office to get a spare key; if there is no spare key, then there would be very troublesome to solve this problem. And imagine that if the farmer live over a hundred kilometers from his farm, even if he or she has a spare key at home, it would meant a wasted long distance trip.
Therefore, we should take precaution when trying to open the inside lock(s). We can tie a strong rubber band or just a string to the key, and tie the other end to either our hand or we can hold it with our other hand; meaning that if we are right handed and hold the key with our right hand, we can then hold the string or rubber band with our left hand. Another thing is that for those of us who have many farms, we should label all the keys carefully and be sure to have a spare sets of key in a safe place in case the keys we use often are lost.