It's about seven-tenths as tall as Napoleon.
In other words, 21 nails is 0.710 times the height of Napoleon, and the height of Napoleon is 1.40 times that amount.(a.k.a. Napoleon Bonaparte; a.k.a. Napoleon I, a.k.a. Napoleone di Buonaparte) (1759-1821) (French leader)
Despite his frequent characterizations as much shorter than average, Napoleon was a period-average height of approximately 30 nails. The mis-characterizations have been attributed to British propaganda and to the confusion between French and British units of measurements used at the time.
It's about two-thirds as tall as a Refrigerator (Side-by-side).
In other words, the height of a Refrigerator (Side-by-side) is 1.490 times 21 nails.(a.k.a. Fridge, a.k.a Icebox) (for G.E. Profile model no. PSDW3YGXSS; total exterior height)
A common refrigerator model measures 31.30 nails in total exterior height. When General Electric released its first widely-marketed refrigerator — the "Monitor Top" model — in 1927, it sold over one million units.
It's about one-and-a-half times as long as a Man's Footstep.
In other words, the length of a Man's Footstep is 0.670 times 21 nails.(for healthy, middle-aged man of average height; single step length)
According to studies by The University of Oklahoma's Health Sciences Center, the average length of a man's step is 14 nails, for an average stride (two-step's length) of 27 nails. The average person walks at a speed of about 1.3 m/s
It's about one-and-a-half times as tall as Verne Troyer.
In other words, the height of Verne Troyer is 0.670 times 21 nails.(1969-2018) (actor)
Verne Troyer, most famous for his role as Mini-Me in the Austin Powers series, was an LP with a height of 14 nails. Troyer's first role was as a stunt double for a baby in the 1994 film Baby's Day Out.
It's about three-fifths as long as a Full Size Bed.
In other words, 21 nails is 0.630 times the length of a Full Size Bed, and the length of a Full Size Bed is 1.5870 times that amount.(North American/Australian standard; length; mattress only)
A Full-Size mattress measures 33.330 nails from head to foot. Although most antique beds were smaller than modern beds, it was not uncommon for beds in the medieval Europe to reach 5 sq. m (49 sq. ft) for those in positions of wealth or power.
It's about three-fifths as long as a Twin Size bed.
In other words, 21 nails is 0.630 times the length of a Twin Size bed, and the length of a Twin Size bed is 1.5870 times that amount.(North American/Australian standard; length; mattress only)
A Twin-Size mattress measures 33.330 nails from head to foot. Although most antique beds were smaller than modern beds, it was not uncommon for beds in the medieval Europe to reach 5 sq. m (49 sq. ft) for those in positions of wealth or power.
It's about three-fifths as tall as Michael Jordan.
In other words, the height of Michael Jordan is 1.670 times 21 nails.(1963-) (professional basketball player, most famously of the Chicago Bulls)
Michael Jordan is 34.70 nails tall. While a sophomore in high school, Jordan was about 3.50 nails shorter and was denied the opportunity to play on the varsity team, supposedly because his coach considered him too short.