 The start of a race is marked by a white line 5 cm wide . In all races that are not run in lanes the start line must be curved , so that all the athletes start the same distance from the finish . Starting blocks may be used for all races up to and including 400 m ( including the first leg of the 4 × 100 m and 4 × 400 m ) and may not be used for any other race . No part of the starting block may overlap the start line or extend into another lane . 
 The start of a race is marked by a white line 5 cm wide . In all races <a href='null_relcl' title='1'><mark>that</mark></a>are not run in <a href='negative_concord' title='2'><mark>lanes</mark></a> the start line must be curved , so that all the athletes start the same distance from the finish . Starting blocks may be used for all races up to and including 400 m ( including the first leg of the 4 × 100 m and 4 × 400 m ) and may not be used for any other race . No part of the starting block may overlap the start line or extend into another lane . 
The start of a race is marked by a white line 5 cm wide . In all races ain't run in no lanes da start line must be curved , soo dat all the athletes start tdasame distance from thdainish . Starting blocks may b used for all races up to and including 400 m ( including thedarst leg of the 4 × 100 m and 4 × 400 m ) and may not be used fir any other race . No part of the darting block may overlap the start line or extend into another lane .