Cambridge Grammar of English Hardback with cd-rom a comprehensive Guide

Immediate communication

339d 

The present simple is used in commentaries on sports events and on public

ceremonies. Commentators use the form to describe what they can see

immediately before them, especially if it forms a sequence of actions which are

completed as the commentator speaks:

[football match commentary]

Shearer to Gillespie … Gillespie 

beats his man on the outside and moves

forward.

A similar use occurs in demonstrations and in instructions:

[a plumber is showing a friend how to mend a tap which is leaking]

You 

put the washer on first, then the metal ring and then you tighten the screw.