Knights are an iconic figure of medieval times. Knights were warriors from the nobility, able to afford the best armour and weapons of the time. A knight costume can be made quite inexpensively with a little work. A spray-painted sweater can convincingly give the appearance of chain mail. The movie "Monty Python and the Holy Grail" used a very similar approach for the costumes worn by the knights.
Spray paint the entire jumper silver or grey. The pattern of yarn in a jumper is very similar to the pattern created by the links in chain mail from medieval times.
Measure the distance between your shoulders. This measurement will be the width of the knight tabard.
Measure the distance from your shoulder to your kneecap while standing. The length of the fabric for the tabard will be double this measurement.
Cut the fabric the length and width you determined from your measurements.
Cut a circle in the centre of the fabric, both length and width wise, about 20 to 25 cm (9 inches) in diameter. This is the head hole for the tabard.
Draw a symbol on the tabard about 10 cm (4 inches) below the head hole using the fabric markers. The top of the symbol should be facing the hole. You can also choose not to include a symbol and leave the tabard blank.
Put on the jumper, trousers, and boots on. Put the tabard over the rest of the costume. The symbol, if one is present, should be in front over your chest.
Place the belt around your waist over the tabard. This will hold it in place.
Common symbols for the tabard of a knight during medieval times would include a cross, fleur-de-lys, a lion, a sword or a shield.