When the primer is dry, knead a ball of linseed oil putty until it is smooth, shape it into a thin strip and press this around the edge of the opening.
Ar ôl i'r paent preimio sychu, mowldiwch belen o byti olew had llin hyd nes ei fod yn llyfn gan greu stribyn tenau a gwasgwch hwn o amgylch ymyl yr agoriad.