(1) I don't quite agree with some previous opinions: I think one is 2cm long and the other is 5mm long, because parallel lines are straight lines, which are infinitely long and have no length, not to mention the length of parallel lines is 5 mm (how long can 5 mm be drawn? )

(2) Primary schools often have such units: 1km300m, which means 1.3km, so I think it is to draw two parallel lines with a distance of 2.5cm.

(3) The painting method is as follows:

Step 1: Draw a straight line.

Step 2: Draw a right angle at one point on this straight line and measure 2.5cm on the other side of the right angle.

Step 3: Draw another right angle at 2.5cm,

So draw two parallel lines with a distance of 25 mm

If you are satisfied, don't forget to reward!