A fid is a conical tool made of wood or bone. It is used to work with rope

Rope

A rope is a length of fibres, twisted or braided together to improve strength for pulling and connecting. It has tensile strength but is too flexible to provide compressive strength...

 and canvas

Canvas

Canvas is an extremely heavy-duty plain-woven fabric used for making sails, tents, marquees, backpacks, and other items for which sturdiness is required. It is also popularly used by artists as a painting surface, typically stretched across a wooden frame...

 in marlinespike seamanship. A fid differs from a marlinspike

Marlinspike

Marlinspike is a tool used in ropework for tasks such as unlaying rope for splicing, untying knots, forming a toggle , or forming a makeshift handle....

 in material and purpose. A marlinespike is used in working with wire rope, may be used to open shackles, and is made of metal. A fid is used to hold open knots and holes in canvas. A fid is used to open the "lays", or strands of rope, synthetic or natural, for splicing

Rope splicing

Rope splicing in ropework is the forming of a semi-permanent joint between two ropes or two parts of the same rope by partly untwisting and then interweaving their strands. Splices can be used to form a stopper at the end of a line, to form a loop or an eye in a rope, or for joining two ropes...

 said line. A variation of the fid, the Gripfid

Gripfid

The Gripfid is an invention of the late knotting expert Stuart Grainger. A small knotter's fid has an added "grip", a hollow shaft that ends near the point with a vee that acts as a jamming cleat....

, is used for ply-split braiding

Ply-split Braiding

Unlike Weaving or many forms of braiding where cloth is formed by threads interlacing in an over-under sequence, Ply-split Braiding is a technique where one twisted cord passes through another twisted cord or cords splitting the plies of the latter cords...

. It adds a jamming cleat to pull a cord back through the cord split by the fid's point.

The term has wider nautical use: e.g. "A little iron fid drops into a slot in the stock (of an anchor)to keep it in place"

In the Canadian Navy, "fid" is also used as a euphemism for a stupid person.

A "fid" is also a unit of measurement equaling approximately 21 or 22 times the rope's diameter. The fid is further divided into a "short" fid and a "long" fid. A short fid is 1/3 the length of the full fid and a long fid is 2/3 the length of the full fid.

This chart shows examples of short, long, and full fid lengths for ropes of almost all diameters.

Fids may come in other shapes, diameters, and lengths, some solid and others hollow. Other than wood, they may also be made of titanium, stainless steel, aluminum, brass, bronze, or copper.


Rope

Diameter (in.)
Rope

Circ. (in.)
Short Fid

(in.)
Long Fid

(in.)

Full Fid

(in.)


3/32"
9/32"
2/3"

1⅓"
2


1/8"
3/8"
7/8"

1¾"
2⅝"


5/32"
15/32"
1

2-1/5"
3-2/7"


3/16"
9/16"
1⅓"

2⅝"
4"


7/32"
21/32"
1½"

3"
4-3/5"


1/4"
3/4"
1¾"

3½"
5¼"


9/32"
27/32"
2"

4"
6"


5/16"
1"
2-1/5"

4⅜"
6-4/7"


3/8"
1⅛"
2⅝"

5¼"
7⅞"


7/16"
1¼"
3"

6⅛"
9-1/5"


1/2"
1½"
3½"

7"
10½"


9-16"
1¾"
4"

7⅞"
11-4/5"


5/8"
2"
4⅜"

8¾"
13⅛"


11/16"
2¼"
4-4/5"

9⅝"
14-4/9"


3/4"
2¼"
5¼"

10½"
15¾"


7/8"
2¾"
6⅛"

12¼"
18⅜"


1"
3"
7"

14"
21"


1⅛"
3½"
7⅞"

15¾"
23⅝"


1¼"
3¾"
8¾"

17½"
23¼"


1-5/16"
4"
9-1/5"

18⅜"
27-4/7"


1½"
4½"
10½"

21"
31½"


1⅝"
5"
11⅜"

22¾"
34⅛"


1¾"
5½"
12¼"

24½"
36¾"


2"
6"
14"

28"
42"


2⅛"
6¼"
14⅞"

29¾"
44⅝"


2¼"
7"
15¾"

31½"
47¼"


2½"
7½"
17½"

35"
52½"


2⅝"
8"
18⅜"

36¾"
55⅛"


2¾"
8½"
19¼"

38½"
57¾"


3"
9"
21"

42"
63"


3¼"
10"
22¾"

45½"
68¼"

External links

• machovec.com, for a chart of fid lengths
• Animated splice & image of fid in use