Stained new deck have runs between boards

Hi Shirley. You will need to use a paint brush or a foam brush to get in between the boards.

You might try and just run a putty knife or something like that through and knock the runs off of there

You need to always Spray it on not brush or roller that way you get the whole board stained

My guess is you did not let the board acclimate to the surrounds before installation.

You can remove runs with thinner.

Spray it, or HD sells a brush, the handle has threads that screws on a stick - that might work, depending on your board gaps. It beats bending down or kneeling.

Had the same issue! The foam brush worked beautifully!