Answer:
First, in your compass take more than half of the given line, i.e, if the line is 5 centimeters, then in the compass take a length more than five centimeters.
Second, Draw an arc, by keeping the compass needle on one end of the line, and do the same by keeping it on the other end.
Two of the arcs will intersect at a point.
Third, do the same, but in the back-ward direction, as in the below of the line. These two will also intersect.
Lastly, draw a line connecting the intersection of the top and below arcs.
I couldnt add the last pic because of the 5 attachments rule. Like I said in the last rule, just join the two arc intersections.
Thank You
Hope u understood