In this short fire plough / fire plow clip you can see how the wood fibres rub off the blade and base and char and  accumulate into a pile. The fibres are heated up and charred as they are rubbed along the board. The build up of the heat in the pile of fibres causes the wood fibres to ignite and an ember form. This is using Hazel on Poplar.

This video is a few years old but it is still current and valid especially in the current environmental crisis - we should be reducing our use of man made materials and synthetics and one of those is bow drill cordage. I have a pet hate against synthetic bow drill cordage. There is no need to use paracord or other synthetic cords with the bow drill and I have been talking about this for a few years!
This video demonstrates different natural cords and 3 different ways of using natural cords and shows that it isn't difficult!

 A good way of extending an ember (or solar lighting) or catching a spark is using a King Alfred Cake (cramp ball fungus or Daldinia concentrica). A King Alfred Cake is a fungus which grows on dead Ash trees, and when the fungus has died off, they turn black and act like a coal. Only collect them when they have turned black (dead) , not brown (still alive). If dead they  should come off the dead tree quite easily - you may need to prise them off using a knife. You can store  for a very long time as long as there is no moisture otherwise they will go mouldy!

You need to strike the sparks\add the ember\direct the sunlight onto the underside not the smooth outside of the ball.  It only takes a small spark (or ember) to light. You will know when it is lit, as you will see a small red glow. Blow on it and the ember will get larger and it will burn like a coal. You can then place your dry tinder on top, such as dry clematis bark or dead dry grass or bracken. Blow onto the glowing ember, and keep blowing, it will start to smoke and may produce lots of smoke! Keep blowing until the tinder bursts into flame then place your kindling on top.
They will smoulder for quite a long period of time so is a good way to extend an ember if the tinder is damp or you're not quite prepared!

 I don't like the Ferro rod at all and  I now don't encourage the use of Ferro Rods especially in these times of environmental crisis as it is a modern man-made alloy using rare earth metals which have to be mined and the hot sparks are actually very very hot (3000 degree metal shards.) The Ferro rod is an all too common bushcraft tool which is also used as an easy way to teach fire lighting by many bushcraft and outdoor educationalists. Kid's do like Ferro rods due to the sparks - but they are very hot shards of metal! It has it's use for survival situations but I don't agree in their use for an everyday fire lighting tool.

Ferrocerium  is used in many applications such as cigarette lighters - but they only use a small amount unlike ferro rods. 

Please do use common sense if introducing children to fire lighting with ferro rods. The sparks produced from a Ferro Rod are very HOT metal shards and can burn skin and catch things alight (e.g. tents) so children should be supervised when using them.

 A few sets made with very basic tools - shards of flint and slab of slate. Our stone age ancestors were very skilled with stone and could make far better stone tools than these so they would have been more than capable of making friction fire sets with stone tools. As I have found flint is very sharp and even with small pieces of flint like the ones below , it is possible to make friction sets - it just takes a little while longer. The slate (photo 1 ) was very good for processing the hearth board by scraping the wood over the sharp edge and by sawing the wood up and down the edge it made an excellent v notch (better than some I make with a carbon steel knife!)