Imagine the situation: you have lost the keys to your apartment... The first questions that come to mind are: “How will I get home? I lost my keys, how do I open the door? etc. In any, even the most hopeless situation, there are at least two ways out. Our problem also has several solutions. For example, you can call the Ministry of Emergency Situations, and the door will be opened very soon. True, they will hopelessly spoil it with turbines or cutters. Then a new question will arise: “How to spend the night in an apartment without doors?” You won't even be able to leave to correct the situation. Another solution to the problem is to call an emergency lock opener, but is there such a person in your city? Perhaps not. There is, of course, the likelihood that among your acquaintances there will be specialists - "bear cubs", in which case this is the most correct solution to the issue. They will help you open the door of the apartment without a key.
I will describe first how to open the door without a key, for example, in the entrance. Elementary pump-action locks are often installed on the doors of entrances, garage doors and (very rarely!) On the doors of apartments. The keys to such "constipation" are of two types - flat and round. The lock of the type in question opens very quickly. For this you will need a pencil and a hammer. If you do not have a pencil at hand, then break off a branch on the nearest tree that is the same diameter as an ordinary pencil. The hammer can be replaced with an ordinary stone or a piece of brick. Insert a pencil (stick) in and hit it sharply with a hammer (brick). That's it, the first lock is open. True, then you will have to remove and disassemble the lock in order to extract the remains of the wood from it, but this, as Carlson said, is already a trifle - an everyday matter. Let's consider ways to open the door without a key. First of all, you need to understand that there are various types of locking devices, and each of them needs its own approach. How to open some locks, I will tell in this article. Why only some? Because to open, for example, such locking devices as Finnish (“Abloi”), levers (“CERBER”, “Guardian”) and a number of others, you need to have a special tool, certain knowledge and, most importantly, skills. 
Now let's move on to pin-type locks (English, "laser", etc.). How to open a door without a key if a pin locking device is embedded in it? In this case, there are only two options. The first method is called "bump". To open the lock using this method, we need a key that matches the profile of your lock (you can borrow a bunch of keys from your neighbors or look for keys to an office or a summer house on a bunch) and some kind of object for striking (a small stone will do, but it is most convenient to use screwdriver). Insert the key into the hole about three-quarters, with the fingers of your left hand make a slight tightness on the key, and with your right hand hit it with the handle of a screwdriver. The first time is unlikely to succeed, but if you apply perseverance, then you have a chance. Even beginners open locks with the "bump" method after a short practice.
Now we will describe the second way, how to open the pin lock. True, this method is only suitable for "laser machines" (two- and single-row). To do this, we need small pliers, metal scissors and a piece of the metal itself (a tin can do) about 0.5 mm thick. We cut out a plate from metal, corresponding in width to the key. We bend it with pliers: in profile, it should resemble waves or a nail file. We insert it into the lock hole, bring it to the stop with a sharp movement (reminiscent of the “bump” method) and try to gently turn it. This method also requires practice.
So we examined the simplest of the ways to solve the issue of how to open the door without a key. However, in any case, training is necessary. Don't wait until you lose your keys, start exercising now.
Yes, we almost forgot the most important thing: opening other people's doors without the knowledge of the owners is strictly prosecuted by the law of any country! Remember this.
