Pon aquel alfiler en el ramo por si hace viento.

in / on / by (means of transport) / about (after pensar)

to do, to make

to put / to set (the table) / to make (an excuse) / to give, to impose (a fine, a penalty)

the wind

that over there (m.sg., also aquella, aquellos, aquellas, aquello)

if

the bouquet

the pin

in case