the.com/starting block

means A rigid frame with angled footplates that sprinters brace against at the start of a race, giving their legs something solid to explode off of instead of raw dirt or track.

from Simple compound of 'start' plus 'block' — a block being a solid chunk of material, here shaped and fixed to the track. Starting blocks are a relatively modern addition to sprinting; earlier generations of racers dug small holes in cinder tracks with trowels to brace their feet, and adjustable mechanical blocks only became standard (and eventually mandatory in top competition) in the 20th century once track surfaces turned synthetic and officials wanted standardized, fair starts.