What is "jack pins"

Tack \Tack\, n. [OE. tak, takke, a fastening; akin to D. tak a branch, twig, G. zacke a twig, prong, spike, Dan. takke a tack, spike; cf. also Sw. tagg prickle, point, Icel. t[=a]g a willow twig, Ir. taca a peg, nail, fastening, Gael. tacaid, Armor. & Corn. tach; perhaps akin to E. take. Cf. Attach, Attack, Detach, Tag an end, Zigzag.]

1. A small, short, sharp-pointed nail, usually having a broad, flat head.

2. That which is attached; a supplement; an appendix. See Tack, v. t.,

3. --Macaulay. Some tacks had been made to money bills in King Charles's time. --Bp. Burnet. 3. (Naut.)

   1. A rope used to hold in place the foremost lower corners of the courses when the vessel is closehauled (see Illust. of Ship); also, a rope employed to pull the lower corner of a studding sail to the boom.

   2. The part of a sail to which the tack is usually fastened; the foremost lower corner of fore-and-aft sails, as of schooners (see Illust. of Sail).

   3. The direction of a vessel in regard to the trim of her sails; as, the starboard tack, or port tack; -- the former when she is closehauled with the wind on her starboard side; hence, the run of a vessel on one tack; also, a change of direction; as, to take a different tack; -- often used metaphorically.

4. (Scots Law) A contract by which the use of a thing is set, or let, for hire; a lease.
   --Burrill.

5. Confidence; reliance. [Prov. Eng.]
   --Halliwell.

   Tack of a flag (Naut.), a line spliced into the eye at the foot of the hoist for securing the flag to the halyards.

   Tack pins (Naut.), belaying pins; -- also called jack pins.

   To haul the tacks aboard (Naut.), to set the courses.

   To hold tack, to last or hold out.
   --Milton.