Variation
Ratchet type:
Setting by only inserting strap into carrier
Bolt Type:
Setting by fixing strap on carrier with bolt and nut.
Carrier
Rachet Type Carrier
Bolt Type Carrier
Snap Idler is a component to keep chain tensioned. It's engineering plastic made "carrier" hold link plates to prevent chain loosened. As shown in below, there are two types, ratchet type and bolt type.
Ratchet type:
Setting by only inserting strap into carrier
Bolt Type:
Setting by fixing strap on carrier with bolt and nut.
Rachet Type Carrier
Bolt Type Carrier