Individual solar cells are somewhat difficult to solder to. Self-adhesive metal stained-glass tape makes for the easiest soldering job--the tape holds itself in place while you solder. Use electronics solder that contains 2% silver. One side of the cell is (+), the other (-).
rain check (plural rain checks) (idiomatic) Any voucher or note from a merchant to a customer to provide an item the merchant has run out of at a later date for the item's current price, or (in a more literal sense) to provide a service at a later date.
Definition of rain. 1  intransitive verb. 2  1 : to send down rain. 3  2 : to fall as water in drops from the clouds.  3 : to fall like rain soot and ash rained 1  down. transitive verb.  1 : to pour 1  down. 2 : to give or administer abundantly rained blows on his  head.