Take a sheet of galvanized metal.
On one side of the sheet was measured out of 8 mm and a line is drawn.
On the opposite side of the sheet and measured out two lines are drawn at a distance of 8 and 16 mm from the edge.
Bends galvanized sheet edge through an angle of 90 degrees from the line.
Next is folded edge of the sheet by the two lines. You need to bend on the second line from the edge, which is at a distance of 16 mm in the same direction as the bend on the opposite side and also at an angle of 90 degrees.
Now you need to make a bending of the sheet edge along the line of 8 mm in the opposite direction. Bend way to get hooked. This will be a groove for bending the opposite side.
We attach the tube sheet form. This can be done by hand, but it is easier to give a semi-circular shape of the sheet galvanized on any pipe of suitable diameter. Then the future will be more smooth tube.
Insert the first bend in the obtained groove on the opposite side and clench the compound.
Now, one last step. The resulting compound to bend towards the first bend and also riveted. The result is a rigid riveted connection, representing the two hooks that hold each other.
In this manner, and it is tube from a sheet of galvanized metal.