Floor mats are rarely, if ever, placed under the left seat -- the pilot's side -- floor. This is because the rudder and brake pedals may be hindered with the addition of even 2 mm width of a floor mat. This presents an unsafe situation. If the pedals get stuck on the mat, the aircraft may respond in dangerous ways. Should you desire to protect the left seat side of the aircraft, consider having the floor covered in all-weather carpet. This should be done by a professional aircraft mechanic who knows how to position the carpet to not impede the rudder and brake pedals.
If you fly a seaplane or you fly in areas with lots of moisture or precipitation, consider getting a rubber floor mat for the right seat floor. A rubber mat collects water, allowing you to remove the mat and shake out the water from the craft. Take care to find one that has mold-preventative coatings and be sure to shake it out after each flight to prevent moisture buildup under the mat and on the floor.
A mat may be customized or cut down to your specific airplane. For example, the floor pattern in a Citabria -- a bush style aircraft -- is different than a Cessna 172. Measure the floor and use a utility knife to cut out a customized floor mat for your aircraft.
Alternately, order aircraft-specific floor mats from specialized aviation product companies.
