From "The Marlinspike Sailor" by Hervey Garret Smith:1956Also: {Guide to simple ship pulley systems} How much power increase does the rig below give the users? 10x, 12X, 13X,  15X, 16X, 17x, 18x, 20x , 24x etc.? (assuming Zer0 Friction Pulleys, straight lines) This gets into what i call "2Handing" the rig.  Essentially that is what the zrig inset inside the 5/1 is doing.  It is pulling as usual, except both ends pull on lines that go to the load, instead of 1 end 'wasting' it's pull on an anchor.  Then, what if we pulled the Blue in 1 hand down and the RedX up?  What about BrownX up, while pulling Blue down?  What if a horizontal rig, where bodyweight could not be employed?  Some explanation of 2 handing is at : Force Relationships

Super Tighten this Line How many X's Effort?

 Answer: 13x from pulling at Blue Input as people mostly do.  Plus another 5x of any input pull at red X!  If pulling with both arms equally (as equal and opposite reactions) compressing in towards each other; multiplier would be 18x pull of 1 hand (assuming no friction); or 13x from 1 hand + 5x from other. Note: if prusik grab/ yellow hint goes to anchor instead of tying back to own line (like most folks rig it instead); then yield is 10x pull at Blue + 5x Pull at Red X (if any); while the other 3x pull, pulls on anchor and not load! handing the rig by pulling up at BrownX as equal and opposite of pulling down on blue gives a yield of 24x; for the ZRig itself is taken from 3xpull at top, and 2 x pull at bottom; to 4x top and 4x bottom.  The 4x bottom feeds into the 5:1 multiplier in series, so multiplies for 20x output.  Then, that joins the 4x top output in a pairallell connection; so these numbers add (20x + 4x) for 24x 1 hand of pull.Now, that would be on a horizontal rig, where bodyweight couldn't just hang on blue, then the lower hand would have different pull on it from just handpull, but top pull/Blue would have bodyweight used + an equal amount of the lowerhand's pull added to top.  For, the top would have to match the lower hand pull, in excess of bodyweight used.  So that, pulling at blue and red in vertical rig would give 13xbodyweight used + 18x lowerhand/Redpull; but just 18x either hand pull in horizontal rig.  Pulling at Blue and Brown vertically would give 13x bodyweight used + 24x lowerhand/Brown pull; but just 24x in horizontal set rig, where bodyweight isn't used to make upper/Blue pull larger than the lower pull input.