wire in 1/72 scale

Stretched sprue works well, as does fishing line. This has the advantage that once installed, it can be tightened by bringing a still-glowing match up close to the thread.
Another option is lycra thread.

HTH

Colin

how do you glue it?

Stretched sprue can be glued with ordinary solvents/glues that you would use for the rest of the model, fishing line and lycra can be glued with cyanoacrylate (Super Glue)

Can you explain what is "sprue"?
I can´t find it in my dictionaire, so i can´t translate it to Portuguese
I really apreciate it
Thanks

My apologies.
Sprue or Runner is the 'frame' that you cut the model parts from and usually throw away. to stretch it, you light a candle, then hold a piece of sprue ABOVE the flames (about the height of the flame, above the top). Rotate the sprue so that the heat is evenly distributed.
Within seconds, you will feel the heated plastic soften. You now pull the ends of the sprue apart. The further apart the ends, the thinner the 'thread' becomes.
Hold the ends until the thread cools.
IMPORTANT!!!
DO NOT allow the sprue to come into contact with the flame; it will catch fire and the smoke given off is TOXIC.
hope this helps
Colin

great!
thanks
now it all comes clear!!!

i'm working in E.R. and i'm using nylon tread that is use for stiching open wound.you have load of sizes and tread to choose from.

Another alternative for you is 'knitting in elastic' . A very thin elastic that is used on hand knitted clothes. Superglue both ends to the model, it helps if you make very small holes at each end & insert the elastic, then glue it. The beauty of this stuff is, if by accident you touch it, it will stretch & not break. Colour it using a permanant marker pen.