On a technical drawing a centre line is drawn with long broken lines and dots in the gaps between them.

If you look at the drawing, each frame has a centre line drawn on one edge of it.  Where either side of a centre line is the same but reflected it is common practise to simply draw one half.

You need to copy the picture of the frame, cut it out and lay it on your wood, draw around it, then fold the template over along the centre line and draw around it again.  You will then have the correct shape drawn on your wood.

What is a little confusing here is that, to save space on the plan, some of the frames are drawn on their sides.  What is also slightly against normal practise is that a part of the frame just over the centre line has been drawn.  The centre line though remains the line about which the frame is reflected so, in the case of frames 3, 4, 5, 6 and 7 the centre line goes through the rebate for the keel and the centre stringer although the entire rebate is drawn.

I hope that makes sense!

Just to add to what Richard say’s I’d trace round the half shape and transfer the image onto card, then cut that out and draw round it, plenty of ways of skinning a cat !!

Regards Ray