AAA,
A sinnet is really just a repeating series of the same knot, the box and barrel knots mentioned are what tiers call a four stranded crown sennit, that is, a series of four stranded crown knots.
You are probably thinking of a common knot used in macrame, which is made by making a series of square knots around a filler usually made from another two strands (or one strand folded over), this is also commonly tied in gimp or boondogle, check the cobra stich in the same sites that show the box and barrel.
There are many ways to tie a lanyard or fob and, unfortunately, a knot can be known by diferent names and diferent knots can be known by the same name, causing confusion.
If you take some time and look around the sites mentioned earlier on this thread you may find what you want, or maybe something that you like better, knot tying is a fun and interesting hobby.