Questions & Answers about Haltu í handriðið þegar þú ferð niður stigann.
Haltu is the singular imperative of að halda. It means hold! or, in this sentence, hold on to ... when speaking to one person.
So:
- að halda = to hold / keep
- haltu = hold! (said to one person)
- haldið = hold! (said to more than one person)
In Icelandic, commands usually do not need the subject pronoun. The imperative form already shows that you are speaking to you.
So Haltu í handriðið is the normal way to say Hold the handrail / Hold on to the handrail.
You can add þú for emphasis in some contexts, but it is usually unnecessary.