Measure saddle setback and position your cleats

Stand the bike on a flat floor, wheels straight, leaning against a wall or in a work stand. Lay the Steel ruler (or else Tape measure) along the saddle, from nose to tail: it should be level. A spirit level, or a phone level app resting on the ruler, helps a lot.

If the saddle tips nose-down or nose-up, loosen the seatpost head bolt with the Allen keys (or else Multi-tool), correct the angle, then tighten again. A nose-down saddle makes you slide forward and puts weight on your hands.

Turn the cranks so that they point straight up and down. Hang a plumb line, such as a piece of string with a key tied to the end, against the nose of the saddle and let it settle in front of the bottom bracket.

Measure horizontally from the string to the centre of the bottom bracket axle: that is your saddle setback. Write it down before you change anything, so you can always go back.

Sit on the bike as you normally would, in your cycling shoes, with someone holding it upright. Put the cranks level, right foot forward, the ball of your foot on the pedal as when riding.

Hang the plumb line from the front of your kneecap, just below the bony bump: it should fall roughly through the pedal axle, within a centimetre either way. If it falls in front, move the saddle back on its rails; if it falls behind, move it forward. Move it 5 mm at a time and tighten to the specified torque with the Torque wrench.

With clipless pedals, the cleat position follows your foot. With your shoe on, feel for the bump at the base of your big toe and mark it on the side of the shoe with a piece of tape; do the same for the base of your little toe.

Slide the cleat forwards or backwards until that bump sits right above the pedal axle, or a few millimetres in front of it. Set the angle so your foot keeps its natural position, heel neither turned in nor out, then tighten the cleat bolts firmly.

Moving the saddle back lengthens the distance to the bottom bracket, and moving the cleats changes your effective leg length. Recheck your saddle height, heel on the pedal, after every change.

Then ride once or twice before fine-tuning. Pain at the front of the knee can come from a saddle too far forward, numb toes from a cleat too far forward. Change one setting at a time so you know which one helped.