The absence of a welding machine is not a reason to assemble frame structures exclusively from the rail. There are ways that allow you to reliably and accurately connect profile pipes without welding equipment. Let's analyze 5 of them.
- Simple right angle Without welding, a right angle can be obtained by bending the pipe, after making a simple trimming. To do this, at the bend point, it is necessary to make a marking consisting of two parallel transverse lines, the distance between which is equal to the width of the pipe.
This marking is transferred to the sides of the pipe. Then it is necessary with the help of a grinder, making cuts along the marks and edges of the pipe, to cut out the side marked walls. Only one transverse line is left without an incision on the front side.
The cut-out side walls are removed. The left tendril bends outward at a right angle.
Now you need to clean the burrs, and bend the pipe. To make it bend as it should, it should be beaten with a hammer. At the end, it is fixed with a rivet installed through the left tongue.
2. T-shaped pipe connection
For a T-shaped joint, it is necessary to mark on one workpiece with parallel lines on three sides a section corresponding to the width of the pipe to be joined. Then the central front wall is divided in half across, and the sides along.
Now you need to cut the central wall with a grinder to get 2 tabs. The side halves of the walls adjacent to these tendrils are removed. 
Next, the tabs on the pipe are bent at right angles to the outside. At the second pipe from the end, you need to make longitudinal cuts along the edges to the length corresponding to its width. After that, with hammer blows, it can be narrowed to the width of the cut.
Then we hammer the narrowed end into the prepared groove on the first pipe until it stops.
The final rigidity will be given by rivets, glorified through the tabs.
3. A right angle with a 45-degree cut
You can get a right angle by bending the pipe, having previously made 45-degree cuts in it. To do this, the center of the bend is marked on it, which will later become the outer corner. From it, in 2 directions, you need to draw lines at 45 degrees using a square. The same is done on the opposite wall of the pipe.
On the front side of the pipe, the edges of the oblique lines are connected parallel. Then, retreating to the right by 10 mm from the extreme, a third parallel line is drawn. It should be divided in half lengthwise.
The fourth parallel line must be drawn with an indentation of 15 mm to the right of the leftmost one. Then you need to draw the lines between it and the first line.
Now the grinder needs to make incisions along oblique lines from the sides, and cut out the tabs inscribed on the front wall of the pipe. The metal cut from the middle is removed.
The large tongue bends at a right angle for 1 mm from its beginning. You also need to straighten 2 small antennae.
After that, the tube bends, and the small tendrils return back to their original position. Thus, a right angle is obtained, and quite rigid even without the use of rivets.
4.Triple angle On one pipe, it is necessary to draw 2 oblique lines at 45 degrees from one point. The same is done on the opposite wall. Then the lines are connected on the front side. Now you need to cut out the marked parts with a grinder, and bend the pipe.
At the second pipe from the end, 3 longitudinal incisions are made along the edges. Their length should correspond to the width of the pipe. The resulting 2 tabs bend outward at a right angle.
Now you need to dock the second tube with the angle of the curved first one. Then they are fastened with rivets.
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** 5.Right angle connection with wooden mortgages**
To make such a connection, it is necessary to cut the ends of the two tubes at 45 degrees.
Then a wooden rail is hammered into them, and cut off.
Now the pipes with mortgages are bent into a corner, after which they are drilled and tightened with screws.
