From oilseeds (rapeseed, canola, peanuts, sunflower seeds, corn germ and flaxseed) oil can be pressed.
Mostly for extraction the seeds are first crushed, broken or ground.
In wind mills (edge mill, stamp mill) this occurs under large spinning standing side (runner) stones. The flour is then heated to about 35-40 degrees and, in a flat horse hair bag, put in the cavity of a pressing block. With the aid of pile-driving wedges those are squeezed to 300 bar. A kind of wine press is also suitable.
The second pressing after (braking the cake an re)heating to 50-60 degrees can be up to 350 bar.

Formerly labeled as "cold pressed" meant to olive oil that little heat was used. After heating can be obtained more oil, but of inferior quality. By cold pressing the nutritional value remains intact. But the increasingly powerful presses and centrifuges today can harvest in one cold pressing all the oil. "Cold Pressed" or "first cold pressing" is now an outdated label.

The finished cakes are a good feed (for cattle) because they are low in fat (a few percent) and rich in protein.

smoutslaanHundred kilo of flax seed supplies about 27 kilo first stamped oil and 3-4 kilo second gang oil with an oil content of flaxseed of 37-38 percent.

Rapeseed and rapeseed oil are used as fuel for lamps and as cooking oil.
False flax (Camelina sativa) the Celts used already as lamp fuel.
Flaxseed oil also dries and thickens, making it suitable for putty, paint, soap etc.
Oils for special purposes such as paint oil is cold pressed. Much knowledge about this is unfortunately already lost.

A hair is a press mat for a wedge press to strike oil. It is a woven mat with cords of together twisted horsehair. Behind it is a with a leather lace sewn leather cover to protect the mat and to get him out the press.
The flour is done in a Buul. These elongated bag in the form of the hair was formerly of wool, now of filter cloth. This Buul goes into the hair, and the hair is close beaten, put in the press room of the wedge press. This is a wedge-shaped, strong, reinforced block where large narrow wedges are hammered in to beat the oil from the meal. (A reverse placed wedge is the releasing wedge to loosen the construction.)

The hair was made from tail hair of a stallion. That of a mare was unsuitable, weakened by urine. Sometimes white hair was added from a cow's tail. Currently, a combination of nylon and sisal is used.
Sometimes people used press planks of laminated beech wood.

The ancient Greeks left after pressing the olive press cake 20 days to ferment and then squeezed it again. This provides a sharper (olive) oil. Then the cake could still be soaked in warm water for a third pressing (for lamp oil).

You‘ll harvest with a lot of work little oil, but the source is readily available, and on the other hand not used for anything else (if you do not make substitute coffee of them): rosehip seeds.

A Piteba oil press would do well for this exclusive product used for centuries as the "beauty oil" against scars, stretch marks, moles, broken cuticles and wrinkles. The effects you’ll notice only after several months.

It is made from the seeds of Rosa Mosqueta which resembles Rosa Rubiginosa, the Eglantine that grows wild here.

What type a rose bush is you can also see from the thorns. Thorns of dog rose (Rosa canina) curves downwards, field rose (Rosa arvensis) tends to be a bit down and eglantine points right from the stem.

By pressure is meant the force, as opposed to stretch stress, which is applied per unit of surface area. You can press by muscle power, weight, etc. If you try to hit with the same pressure or force a coin or a nail into a wood block, you notice that 'per unit area’ is very important.
We have advantage to apply this knowledge.

By reducing the surface (sharpening, grinding), e.g. with a thumb nail, a pole, an arrowhead, a sharp knife... has the same pressure a greater effect.
Conversely, the distribution of the pressure will also be useful, e.g. with snowshoes (vs. Stiletto), a ladder laid on the ice, caterpillars, extra wide or double tractor tires, a strut with widened ends, a bed of nails. A bridge, jetty or shelf weighing at one point or over the entire length can make a big difference.
On a surface with area A, a force F is uniformly exerted, then the pressure p is given by: P = F / A
Even air has weight and exerts pressure.
Atmosphere is an obsolete unit of pressure, for the average sea level pressure:
1 atm = 760 mm Hg, or millimeters of mercury (column)
The air pressure (at sea level) is about 100,000 Pa (Pascal) (101,325 kPa). 1 Pa = 1 N/m2
1 bar corresponds to 100 000 Pa. The word bar comes from the Greek word baros: weight.
So approximate (!) is 1 bar = 1 atm = 1 kgf / cm²
The carbon dioxide in a (solid) bottle of sparkling wine has a pressure of 5 to 6 bar. Oil pressing or hammering we do at about 300 bar. In order to make usable biogas we bring it under pressure. In boilers and steam boilers we provide valves to escape (over) pressure by steam.
Bara, stands for absolute pressure, and (baro or) barg (bar gauge), for overpressure.
With pumps and bellows we use over-and under pressure.

Divers (who dived without dive computer) were teached a sizable chunk of this during their training.