Half cut laces
From your pocket you remove a pair of shoe laces which are wrapped in a paper tube, you remove the laces and pass one to each of two spectators, informing them that the laces have been ‘doctored’ to assist in creating an illusion, asking them to inspect to see if they can see anything strange about the laces.
They notice nothing strange so you proceed to show what you mean by placing the ends of the laces through the paper tube so that the tube is now at the centre of the laces and handing someone a pair of scissors, you have them cut through the paper tube/laces at its centre thus giving you a pair of cut ends in each hand. Now momentarily touching the cut ends together and in an instant you restore the laces to their uncut state and hand them back for inspection.
Just as they think the effect is over you pick up the two cut pieces of paper tube and touching them together and with a gentle rub you visually restore the tube to its original state and hand this for inspection also.