I'm certainly no pro-arborist but I would say that there are two reasons for not using screw_link_s in climbing systems: 1) a rope moving through the screw_link_ could cause the gate to turn with it, undoing the gate...

I've found when using screw_link_s for non-personal-safety fixings (I've used Maillon Rapide _link_s) the _link_s can be very hard to undo, particularly with wet/cold hands and if they've been done up too tight.



A friendly observation - As I read the comments from the many pros an ams on the board something struck me...Aren't the above statements contradictory?

The NFPA,(National Fire Protection Agency)who regulate ALL safety and operations concerned with high angle rescue, require screwgate biners. Until recently, they required those biners to also be steel.

IMO, if a screwgate is closed properly, it should never come open, and even if it does, think about the strength rating on your biners. I'm sure someone has mentioned this on this forum before, but...
1 kN is equal to approx 224.8 foot pounds of force. I don't have a biner rated less than 25 kN. or 5,620 lbf.(closed) The same biner is rated 11kN or 2,023.2 lbf with the gate open - not unscrewed, but wide open.