Idiom:

prim and proper (appropriate )

Hit the book:

Edge

Entrapment

Shut-off button

Secure

Unaware of

Be prone to

Mitten

Shoelace

Drawstring

Complex

Avoid the Steps' Edges

You should avoid the edges of an escalator's steps when riding one as possible entrapment may occur. Every escalator is designed to show the edge where you may be entrapped. The yellow lines in the sides of the escalator steps show the place where you should put your feet to avoid any entrapments.