Renegade Wheelsmith — ruling 1

This is a triggered ability, not an activated ability. It doesn’t allow you to tap Renegade Wheelsmith whenever you want; rather, you need some other way of tapping it, such as by attacking or crewing a Vehicle.

Renegade Wheelsmith — ruling 2

For the ability to trigger, Renegade Wheelsmith has to actually change from untapped to tapped. If an effect attempts to tap it, but it was already tapped at the time, this ability won’t trigger.

Renegade Wheelsmith : règles, fonctionnement et interactions (MTG)

Renegade Wheelsmith is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Whenever this creature becomes tapped, target creature can't block this turn.

How it works : Renegade Wheelsmith

Original English text — Wizards of the Coast / Scryfall

#1February 9, 2017· Wizards of the Coast
This is a triggered ability, not an activated ability. It doesn’t allow you to tap Renegade Wheelsmith whenever you want; rather, you need some other way of tapping it, such as by attacking or crewing a Vehicle.
No other card is named in this ruling.
#2February 9, 2017· Wizards of the Coast
For the ability to trigger, Renegade Wheelsmith has to actually change from untapped to tapped. If an effect attempts to tap it, but it was already tapped at the time, this ability won’t trigger.
No other card is named in this ruling.