Editing Block and tackle (section)

===Rove to disadvantage===
The mechanical advantage of any tackle can be increased by interchanging the fixed and moving blocks so the rope is attached to the moving block and the rope is pulled in the direction of the lifted load. In this case the block and tackle is said to be "rove to advantage."<ref>[http://www.sccheadquarters.com/UserData/root/Files/Training/Specialisations/Seamanship/Chapter%205%20-%20General%20Rigging.pdf sccheadquarters.com seamanship reference] {{webarchive |url=https://web.archive.org/web/20111111234251/http://www.sccheadquarters.com/UserData/root/Files/Training/Specialisations/Seamanship/Chapter%205%20-%20General%20Rigging.pdf |date=November 11, 2011 }}</ref>

* "Rove to advantage" – where the pull on the rope is in the same direction as that in which the load is to be moved. The hauling part is pulled from the moving block.<ref name="advantage">{{cite book |title=Handbook of Rigging: For Construction and Industrial Operations |publisher=McGraw-Hill Professional |isbn=978-0-07-149301-7 |last=MacDonald |first=Joseph A |date=14 January 2009 |pages=376 |quote=Tackle may be rigged to advantage - where the pull on the rope is in the same direction as that in which the load is to be moved; or it may be rigged to disadvantage - where the pull on the rope is in the opposite direction of that in which the load is to be moved}}</ref>
* "Rove to disadvantage" – where the pull on the rope is in the opposite direction to that in which the load is to be moved. The hauling part is pulled from the fixed block.<ref name="advantage" />

Diagram 3 shows three rope parts supporting the load ''W'', which means the tension in the rope is ''W/3''. Thus, the mechanical advantage is three-to-one.

By adding a pulley to the fixed block of a gun tackle the direction of the pulling force is reversed though the mechanical advantage remains the same, Diagram 3a. This is an example of the Luff tackle.
<gallery>
Image:Pulley2.svg|Diagram 3:  The gun tackle "rove to advantage" has the rope attached to the moving pulley. The tension in the rope is ''W/3'' yielding an advantage of three.
Image:Pulley2a.svg|Diagram 3a: The Luff tackle adds a fixed pulley "rove to disadvantage."  The tension in the rope remains ''W/3'' yielding an advantage of three.
</gallery>

The decision of which to use depends on pragmatic considerations for the total [[ergonomics]] of working with a particular situation. Reeving to advantage is the most efficient use of equipment and resources. For example, if the load is to be hauled parallel to the ground, reeving to advantage enables the pulling force to be in the direction of the load movement, allowing obstacles to be managed more easily.

Reeving to disadvantage adds an extra sheave to change the direction of the pulling line to a potentially more ergonomic direction, which increases friction losses without improving the velocity ratio. Situations in which reeving to disadvantage may be more desirable include lifting from a fixed point overhead--the additional pulley allows pulling downwards instead of upwards so that the weight of the lifter can offset the weight of the load, or allows pulling sideways, enabling multiple lifters to combine effort.